Thermopower of Two-Dimensional Electrons at $\nu$ = 3/2 and 5/2 (2010)
Chickering, W. E., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The longitudinal thermopower of ultra-high mobility two-dimensional electrons has been measured at both zero magnetic field and at high fields in the compressible metallic state at filling factor...
Quantum Hall Exciton Condensation at Full Spin Polarization (2010)
Finck, A. D. K., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Using Coulomb drag as a probe, we explore the excitonic phase transition in quantum Hall bilayers at ν_T = 1 as a function of Zeeman energy E_Z. The critical layer separation (d/ℓ)_c for exciton...
Khodas, M., Chiang, H. -S., Hatke, A. T., Zudov, M. A., Vavilov, M. G., Pfeiffer, L. N., ...
We report on magneto-oscillations in differential resistivity of a two-dimensional electron system subject to intense microwave radiation. The period of these oscillations is determined not only by...
Observation of a One-Dimensional Spin-Orbit Gap in a Quantum Wire (2009)
Quay, C. H. L., Hughes, T. L., Sulpizio, J. A., Pfeiffer, L. N., Baldwin, K. W., West, K. W., ...
Understanding the flow of spins in magnetic layered structures has enabled an increase in data storage density in hard drives over the past decade of more than two orders of magnitude1. Following...
Quantum Hall Exciton Condensation at Full Spin Polarization (2009)
Finck, A. D. K., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Using Coulomb drag as a probe, we explore the excitonic phase transition in quantum Hall bilayers at nu=1 as a function of Zeeman energy, E_Z. The critical layer separation d/l for exciton...
Willett, R. L., Pfeiffer, L. N., West, K. W.
It is a theoretical conjecture that 5/2 fractional quantum Hall state charge e/4 excitations may obey exotic non-Abelian statistics. In edge state interference these purported non-Abelian...
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Tunneling measurements on 2D electron gases at high magnetic field reveal a qualitative difference between the two spin sublevels of the lowest Landau level. While the tunneling current–voltage...
Noh, Hwayong, Lee, S., Chun, S. H., Kim, H. C., Pfeiffer, L. N., West, K. W.
Hall effect of two-dimensional holes that are spin-polarized by a strong parallel magnetic field was explored with a small tilt angle. The Hall resistivity increases nonlinearly with the magnetic...
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Tunneling measurements on 2D electron gases at high magnetic field reveal a qualitative difference between the two spin sublevels of the lowest Landau level. While the tunneling current-voltage...
Pinning mode resonance of a Skyrme crystal near Landau level filling factor $\nu$=1 (2009)
Zhu, Han, Sambandamurthy, G., Chen, Yong P., Jiang, Pei-Hsun, Engel, Lloyd, Tsui, D. C., ...
Microwave pinning-mode resonances found around integer quantum Hall effects, are a signature of crystallized quasiparticles or holes. Application of in-plane magnetic field to these crystals,...
Li, Wanli, Vicente, C. L., Xia, J. S., Pan, W., Tsui, D. C., Pfeiffer, L. N., ...
The quantum Hall plateau transition was studied at temperatures down to 1 mK in a random alloy disordered high mobility two-dimensional electron gas. A perfect power-law scaling with \kappa=0.42 was...
Engineering artificial graphene in a two-dimensional electron gas (2009)
Gibertini, M., Singha, A., Pellegrini, V., Polini, M., Vignale, G., Pinczuk, A., ...
At low energy, electrons in doped graphene sheets behave like massless Dirac fermions with a Fermi velocity which does not depend on carrier density. Here we show that modulating a two-dimensional...
Wigner Crystallization in a Quasi-3D Electronic System (2009)
Piot, B. A., Jiang, Z., Dean, C. R., Engel, L. W., Gervais, G., Pfeiffer, L. N., ...
When a strong magnetic field is applied perpendicularly (along z) to a sheet confining electrons to two dimensions (x-y), highly correlated states emerge as a result of the interplay between...
Current-induced nuclear-spin activation in a two-dimensional electron gas (2009)
Dean, C. R., Piot, B. A., Gervais, G., Pfeiffer, L. N., West, K. W.
Electrically detected nuclear magnetic resonance was studied in detail in a two-dimensional electron gas as a function of current bias and temperature. We show that applying a relatively modest...
Role of electron-electron interactions in nonlinear transport in 2D electron systems (2009)
Hatke, A. T., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We study the temperature evolution of the non-linear oscillatory magnetoresistance in a high-mobility two-dimensional electron system subject to a strong dc electric field. We find that the decay of...
Edge-State Velocity and Coherence in a Quantum Hall Fabry-Perot Interferometer (2009)
McClure, D. T., Zhang, Yiming, Rosenow, B., Levenson-Falk, E. M., Marcus, C. M., Pfeiffer, L. N., ...
We investigate nonlinear transport in electronic Fabry-Perot interferometers in the integer quantum Hall regime. For interferometers sufficiently large that Coulomb blockade effects are absent, a...
Phonon-induced Resistance Oscillations in Very-high Mobility 2D Electron Systems (2009)
Hatke, A. T., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We report on temperature dependence of acoustic phonon-induced resistance oscillations in very high mobility two-dimensional electron systems. We observe that the temperature dependence is...
Temperature Dependence of Microwave Photoresistance in 2D Electron Systems (2009)
Hatke, A. T., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We report on the temperature dependence of microwave-induced resistance oscillations in high-mobility two-dimensional electron systems. We find that the oscillation amplitude decays exponentially...
Zhang, Yiming, McClure, D. T., Levenson-Falk, E. M., Marcus, C. M., Pfeiffer, L. N., West, K. W.
Two distinct types of magnetoresistance oscillations are observed in two electronic Fabry-Perot interferometers of different sizes in the integer quantum Hall regime. Measuring these oscillations as...
Local magnetization fluctuations in superconducting glasses resolved by Hall sensors (2008)
Lefebvre, J., Hilke, M., Altounian, Z., West, K. W., Pfeiffer, L. N.
We report on magnetization measurements performed on a series of Fe$_{x}$Ni$_{1-x}$Zr$_{2}$ superconducting metallic glasses with $0\leq x\leq0.5$ using the Hall effect of a nearby 2-dimensional...
Pinning mode resonances of 2D electron stripe phases: Effect of in-plane magnetic field (2008)
Zhu, Han, Sambandamurthy, G., Engel, L. W., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We study the anisotropic pinning-mode resonances in the rf conductivity spectra of the stripe phase of 2D electron systems (2DES) around Landau level filling 9/2, in the presence of an in-plane...
Microwave Photoresistance in dc-driven 2D Systems at Cyclotron Resonance Subharmonics (2008)
Hatke, A. T., Chiang, H. -S., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We study microwave photoresistivity oscillations in a high mobility two-dimensional electron system subject to strong dc electric fields. We find that near the second subharmonic of the cyclotron...
Observation of a Fractional Quantum Hall State at $\nu=1/4$ in a Wide GaAs Quantum Well (2008)
Luhman, D. R., Pan, W., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We report the observation of an even-denominator fractional quantum Hall (FQH) state at $\nu=1/4$ in a high quality, wide GaAs quantum well. The sample has a quantum well width of 50 nm and an...
Charge Imbalance and Bilayer 2D Electron Systems at $\nu_T = 1$ (2008)
Champagne, A. R., Finck, A. D. K., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We use interlayer tunneling to study bilayer 2D electron systems at $\nu_T = 1$ over a wide range of charge density imbalance, $\Delta \nu =\nu_1-\nu_2$, between the two layers. We find that the...
Dorozhkin, S. I., Pechenezhskiy, I. V., Pfeiffer, L. N., West, K. W., Umansky, V., Von Klitzing, K., ...
We observe in state-of-the-art GaAs based 2D electron systems microwave induced photo-current and photo-voltage oscillations around zero as a function of the applied magnetic field. The photo-signals...
Willett, R. L., Pfeiffer, L. N., West, K. W.
A standing problem in low dimensional electron systems is the nature of the 5/2 fractional quantum Hall state: its elementary excitations are a focus for both elucidating the state's properties and...
Contrasting Behavior of the 5/2 and 7/3 Fractional Quantum Hall Effect in a Tilted Field (2008)
Dean, C. R., Piot, B. A., Hayden, P., Sarma, S. Das, Gervais, G., Pfeiffer, L. N., ...
Using a tilted field geometry, the effect of an in-plane magnetic field on the even denominator nu = 5/2 fractional quantum Hall state is studied. The energy gap of the nu = 5/2 state is found to...
Finck, A. D. K., Champagne, A. R., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The area and perimeter dependence of the Josephson-like interlayer tunneling signature of the coherent $\nu_T=1$ quantum Hall phase in bilayer two-dimensional electron systems is examined....
Saturation of intersubband transitions in p-doped GaAs/AlGaAs quantum wells (2008)
Steed, R., Matthews, M., Plumridge, J., Frogley, M., Phillips, C., Ikonic, Z., ...
Optical saturation experiments have been performed on hh1-hh2 intersubband transitions in two samples of p-doped GaAs/AlGaAs quantum wells. The transitions had energies of 183 and 160 meV and the...
Non-linear magnetotransport in microwave-illuminated two-dimensional electron systems (2008)
Hatke, A. T., Chiang, H. -S., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We study magnetoresistivity oscillations in a high-mobility two-dimensional electron system subject to both microwave and dc electric fields. First, we observe that the oscillation amplitude is a...
Quasiparticle Tunneling in the Fractional Quantum Hall State at \nu = 5/2 (2008)
Radu, Iuliana P., Miller, J. B., Marcus, C. M., Kastner, M. A., Pfeiffer, L. N., West, K. W.
Theory predicts that quasiparticle tunneling between the counter-propagating edges in a fractional quantum Hall state can be used to measure the effective quasiparticle charge e* and dimensionless...
Observation of pinning mode of stripe phases of 2D systems in high Landau levels (2008)
Sambandamurthy, G., Lewis, R. M., Zhu, Han, Chen, Y. P., Engel, L. W., Tsui, D. C., ...
We study the radio-frequency diagonal conductivities of the anisotropic stripe phases of higher Landau levels near half integer fillings. In the hard direction, in which larger dc resistivity occurs,...
Evidence for a Finite-Temperature Phase Transition in a Bilayer Quantum Hall System (2008)
Champagne, A. R., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We study the Josephson-like interlayer tunneling signature of the strongly correlated nuT=1 quantum Hall phase in bilayer two-dimensional electron systems as a function of the layer separation,...
Anisotropic modification of the effective hole $g$-factor by electrostatic confinement (2008)
Koduvayur, S. P., Rokhinson, L. P., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We investigate effects of lateral confinement on spin splitting of energy levels in 2D hole gases grown on [311] GaAs. We found that lateral confinement enhances anisotropy of spin splitting relative...
Intrinsic Gap of the nu=5/2 Fractional Quantum Hall State (2008)
Dean, C. R., Piot, B. A., Hayden, P., Sarma, S. Das, Gervais, G., Pfeiffer, L. N., ...
The fractional quantum Hall effect is observed at low field, in a regime where the cyclotron energy is smaller than the Coulomb interaction. The nu=5/2 excitation gap is measured to be 262+/-15 mK at...
Experimental studies of the fractional quantum Hall effect in the first excited Landau level (2008)
Pan, W., Xia, J. S., Stormer, H. L., Tsui, D. C., Vicente, C., Adams, E. D., ...
We present a spectrum of experimental data on the fractional quantum Hall effect (FQHE) states in the first excited Landau level, obtained in an ultrahigh mobility two-dimensional electron system...
Detection of spin polarization in quantum point contacts (2008)
Rokhinson, L. P., Pfeiffer, L. N., West, K. W.
We use spatial spin separation by a magnetic focusing technique to probe the polarization of quantum point contacts. The point contacts are fabricated from p-type GaAs/AlGaAs heterostructures. A...
Anisotropic modification of the effective hole g factor by electrostatic confinement (2008)
Koduvayur, S. P., Rokhinson, L. P., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We investigate effects of lateral confinement on spin splitting of energy levels in 2D hole gases grown on [311] GaAs. We found that lateral confinement enhances anisotropy of spin splitting relative...
Soft spin wave around $\nu$=1: evidence for a magnetic instability in skyrmion systems. (2008)
Gallais, Yann, Yan, Jun, Pinczuk, A., Pfeiffer, L. N., West, K. W.
The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the...
Soft spin wave around $\nu$=1: evidence for a magnetic instability in skyrmion systems. (2008)
Gallais, Yann, Yan, Jun, Pinczuk, A., Pfeiffer, L. N., West, K. W.
The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the...
Soft spin wave around $\nu$=1: evidence for a magnetic instability in skyrmion systems. (2008)
Gallais, Yann, Yan, Jun, Pinczuk, A., Pfeiffer, L. N., West, K. W.
The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the...
Soft spin wave around $\nu$=1: evidence for a magnetic instability in skyrmion systems. (2008)
Gallais, Yann, Yan, Jun, Pinczuk, A., Pfeiffer, L. N., West, K. W.
The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the...
Disappearance of the metal-like behavior in GaAs two-dimensional holes below 30 mK (2007)
Huang, Jian, Xia, J. S., Tsui, D. C., Pfeiffer, L. N., West, K. W.
The zero-field temperature-dependence of the resistivity of two-dimensional holes are observed to exhibit two qualitatively different characteristics for a fixed carrier density for which only the...
Dean, C. R., Piot, B. A., Pfeiffer, L. N., West, K. W., Gervais, G.
A study of the resistively detected nuclear magnetic resonance (RDNMR) lineshape in the vicinity of $\nu=1$ was performed on a high-mobility 2D electron gas formed in GaAs/AlGaAs. In higher Landau...
Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields (2007)
Zhang, W., Zudov, M. A., Pfeiffer, L. N., West, K. W.
Using dc excitation to spatially tilt Landau levels, we study resonant acoustic phonon scattering in two-dimensional electron systems. We observe that dc electric field strongly modifies phonon...
Transport and percolation in a low-density high-mobility two-dimensional hole system (2007)
Manfra, M. J., Hwang, E. H., Sarma, S. Das, Pfeiffer, L. N., West, K. W., Sergent, A. M.
We present a study of the temperature and density dependence of the resistivity of an extremely high quality two-dimensional hole system grown on the (100) surface of GaAs. For high densities in the...
Stone, K., Yang, C. L., Yuan, Z. Q., Du, R. R., Pfeiffer, L. N., West, K. W.
Using very-high mobility GaAs/AlGaAs 2D electron Hall bar samples, we have experimentally studied the photoresistance/photovoltaic oscillations induced by microwave irradiation in the regime where...
Evidence for a finite temperature phase transition in a bilayer quantum Hall system (2007)
Champagne, A. R., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We study the Josephson-like interlayer tunneling signature of the strongly correlated $\nu_T = 1$ quantum Hall phase in bilayer two-dimensional electron systems as a function of the layer separation,...
Soft Spin Wave Near nu=1: Evidence for a Magnetic Instability in Skyrmion Systems (2007)
Gallais, Y., Yan, J., Pinczuk, A., Pfeiffer, L. N., West, K. W.
The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the...
Aharonov-Bohm-Like Oscillations in Quantum Hall Corrals (2007)
Godfrey, M. D., Jiang, P., Kang, W., Simon, S. H., Baldwin, K. W., Pfeiffer, L. N., ...
Experimental study of quantum Hall corrals reveals Aharonov-Bohm-Like (ABL) oscillations. Unlike the Aharonov-Bohm effect which has a period of one flux quantum, $\Phi_{0}$, the ABL oscillations...
Shot-Noise-Limited Operation of a Fast Quantum-Point-Contact Charge Sensor (2007)
Thalakulam, Madhu, Xue, W. W., Pan, Feng, Ji, Z., Stettenheim, J., Pfeiffer, Loren, ...
We have operated a quantum point contact (QPC) charge detector in a radio frequency (RF) mode that allows fast charge detection in a bandwidth of tens of megahertz. We find that the charge...
High Resolution Spectroscopy of Two-Dimensional Electron Systems (2007)
Dial, O. E., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
Spectroscopic methods involving the sudden injection or ejection of electrons in materials are a powerful probe of electronic structure and interactions. These techniques, such as photoemission and...
Fractional Quantum Hall Effect in the Second Landau Level (2007)
Choi, H. C., Kang, W., Sarma, S. Das, Pfeiffer, L. N., West, K. W.
We present activation gap measurements of the fractional quantum Hall effect (FQHE) in the second Landau level. Signatures for 14 (5) distinct incompressible FQHE states are seen in a high (low)...
Quantum Lifetime of Two-Dimensional Holes (2007)
Eisenstein, J. P., Syphers, D., Pfeiffer, L. N., West, K. W.
The quantum lifetime of two-dimensional holes in a GaAs/AlGaAs double quantum well is determined via tunneling spectroscopy. At low temperatures the lifetime is limited by impurity scattering but at...
Current Noise in Quantum Point Contacts (2007)
DiCarlo, L., Zhang, Yiming, McClure, D. T., Reilly, D. J., Marcus, C. M., Pfeiffer, L. N., ...
We present measurements of current noise in quantum point contacts as a function of source-drain bias, gate voltage, and in-plane magnetic field. At zero bias, Johnson noise provides a measure of the...
Scanning-probe spectroscopy of semiconductor donor molecules (2007)
Kuljanishvili, I., Kayis, C., Harrison, J. F., Piermarocchi, C., Kaplan, T. A., Tessmer, S. H., ...
Semiconductor devices continue to press into the nanoscale regime, and new applications have emerged for which the quantum properties of dopant atoms act as the functional part of the device,...
Impact of spin-orbit coupling on quantum Hall nematic phases (2007)
Manfra, M. J., De Picciotto, R., Jiang, Z., Simon, S. H., Pfeiffer, L. N., West, K. W., ...
Anisotropic charge transport is observed in a two-dimensional (2D) hole system in a perpendicular magnetic field at filling factors nu=7/2, nu=11/2, and nu=13/2 at low temperature. In stark contrast,...
Simple-layered high mobility field effect heterostructured two-dimensional electron device (2007)
Willett, R. L., Pfeiffer, L. N., West, K. W.
We present a two-dimensional electron heterostructure field effect device of simplistic design and ease of fabrication that displays high mobility electron transport. This is accomplished using a...
Mesoscopic structures and 2D hole systems in fully field effect controlled heterostructures (2007)
Willett, R. L., Manfra, M. J., Pfeiffer, L. N., West, K. W.
Two fundamental extensions to the function of previously described fully field effect two-dimensional (2D) electron heterostructures are presented: First, using the same basic heterostructure design...
Confinement of fractional quantum Hall states in narrow conducting channels (2007)
Willett, R. L., Manfra, M. J., Pfeiffer, L. N., West, K. W.
Confinement of small-gapped fractional quantum Hall states facilitates quasiparticle manipulation and is an important step towards quasiparticle interference measurements. Demonstrated here is...
Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2 (2007)
Miller, J. B., Radu, I. P., Zumbuhl, D. M., Levenson-Falk, E. M., Kastner, M. A., Marcus, C. M., ...
Recent theories suggest that the excitations of certain quantum Hall states may have exotic braiding statistics which could be used to build topological quantum gates. This has prompted an...
Spin Transition in the Half-Filled Landau Level (2007)
Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The transition from partial to complete spin polarization of two-dimensional electrons at half filling of the lowest Landau level has been studied using resistively detected nuclear magnetic...
Zhang, W., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We report on magnetotransport measurements in a high-mobility two-dimentional electron system subject simultaneously to AC (microwave) and DC (Hall) fields. We find that DC excitation affects...
Astability and negative differential resistance of the Wigner solid (2007)
Csathy, G. A., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We report spontaneous narrow band oscillations in the high field Wigner solid. These oscillations are similar to the recently seen and yet unexplained oscillations in the reentrant integer quantum...
Interaction effects in the transport of two-dimensional holes in GaAs (2006)
Huang, Jian, Novikov, D. S., Tsui, D. C., Pfeiffer, L. N., West, K. W.
The power-law increase of the conductivity with temperature in the nominally insulating regime, recently reported for the dilute two-dimensional holes [cond-mat/0603053], is found to systematically...
Absorption in the fractional quantum Hall regime: trion dichroism and spin polarization (2006)
Groshaus, J. G., Plochocka-Polack, P., Rappaport, M., Umansky, V., Bar-Joseph, I., Dennis, B. S., ...
We present measurements of optical interband absorption in the fractional quantum Hall regime in a GaAs quantum well in the range 0 < nu < 1. We investigate the mechanism of singlet trion absorption,...
Spin Transition in the Half-Filled Landau Level (2006)
Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The transition from partial to complete spin polarization of two-dimensional electrons at half filling of the lowest Landau level has been studied using resistively-detected nuclear magnetic...
Magnetotransport in a two-dimensional electron system in dc electric fields (2006)
Zhang, W., Chiang, H. -S., Zudov, M. A., Pfeiffer, L. N., West, K. W.
We report on nonequilibrium transport measurements in a high-mobility two-dimensional electron system subject to weak magnetic field and dc excitation. Detailed study of dc-induced...
Dorozhkin, S. I., Smet, J. H., Von Klitzing, K., Pfeiffer, L. N., West, K. W.
The magnetoresistance oscillations, which occur in a two-dimensional electron system exposed to strong microwave radiation when the microwave frequency $\omega$ coincides with the n-th subharmonic of...
Spin excitations in the Fractional Quantum Hall regime at $\nu\lesssim1/3$ (2006)
Gallais, Y., Kirschenmann, T. H., Hirjibehedin, C. F., Dujovne, I., Pinczuk, A., Pfeiffer, L. N., ...
We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors $\nu\lesssim1/3$. A spin mode is observed below the Zeeman energy. The filling factor...
Transition from Free to Interacting Composite Fermions away from $\nu$=1/3 (2006)
Gallais, Y., Kirschenmann, T. H., Dujovne, I., Hirjibehedin, C. F., Pinczuk, A., Dennis, B. S., ...
Spin excitations from a partially populated composite fermion level are studied above and below $\nu=1/3$. In the range $2/7
Yuan, Z. Q., Yang, C. L., Du, R. R., Pfeiffer, L. N., West, K. W.
The microwave (MW) photoresistance has been measured on a high-mobility two-dimensional electron gas patterned with a shallow triangular antidot lattice, where both the MW-induced resistance...
Luin, S., Pellegrini, V., Pinczuk, A., Dennis, B. S., Pfeiffer, L. N., West, K. W.
Resonant Rayleigh scattering of light from electrons confined in gallium arsenide double quantum wells displays significant changes at temperatures that are below one degree Kelvin. The Rayleigh...
Disorder mediated splitting of the cyclotron resonance in two-dimensional electron systems (2006)
Henriksen, E. A., Syed, S., Wang, Y. -J., Stormer, H. L., Pfeiffer, L. N., West, K. W.
We perform a direct study of the magnitude of the anomalous splitting in the cyclotron resonance (CR) of a two-dimensional electron system (2DES) as a function of sample disorder. In a series of...
Melting of a 2D quantum electron solid in high magnetic field (2006)
Yong P. Chen, G. Sambandamurthy, Z. H. Wang, R. M. Lewis, L. W. Engel, D. C. Tsui, ...
Bichromatic Microwave Photoresistance of Two-Dimensional Electron System (2006)
Zudov, M. A., Du, R. R., Pfeiffer, L. N., West, K. W.
We explore experimentally bichromatic (frequencies $\omega_1$ and $\omega _2$) photoresistance of a two-dimensional electron system in the regimes of microwave-induced resistance oscillations and...
Transition from Free to Interacting Composite Fermions away from $\nu$=1/3 (2006)
Gallais, Y., Kirschenmann, T. H., Dujovne, I., Hirjibehedin, C. F., Pinczuk, A., Dennis, B. S., ...
Spin excitations from a partially populated composite fermion level are studied above and below $\nu=1/3$. In the range $2/7
A system for measuring auto- and cross-correlation of current noise at low temperatures (2006)
DiCarlo, L., Zhang, Y., McClure, D. T., Marcus, C. M., Pfeiffer, L. N., West, K. W.
We describe the construction and operation of a two-channel noise detection system for measuring power and cross spectral densities of current fluctuations near 2 MHz in electronic devices at low...
Shot-Noise Signatures of 0.7 Structure and Spin in a Quantum Point Contact (2006)
DiCarlo, L., Zhang, Y., McClure, D. T., Reilly, D. J., Marcus, C. M., Pfeiffer, L. N., ...
We report simultaneous measurement of shot noise and dc transport in a quantum point contact as a function of source-drain bias, gate voltage, and in-plane magnetic field. Shot noise at zero field...
Melting of a 2D Quantum Electron Solid in High Magnetic Field (2006)
Chen, Yong P., Sambandamurthy, G., Wang, Z. H., Lewis, R. M., Engel, L. W., Tsui, D. C., ...
The melting temperature ($T_m$) of a solid is generally determined by the pressure applied to it, or indirectly by its density ($n$) through the equation of state. This remains true even for helium...
Spin excitations in the Fractional Quantum Hall regime at $\nu\lesssim1/3$ (2006)
Gallais, Y., Kirschenmann, T. H., Hirjibehedin, C. F., Dujovne, I., Pinczuk, A., Pfeiffer, L. N., ...
We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors $\nu\lesssim1/3$. A spin mode is observed below the Zeeman energy. The filling factor...
Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Resistively detected nuclear magnetic resonance (NMR) measurements on 2D electron systems near the nu=1 quantum Hall state are reported. In contrast to recent results of Gervais et al. [Phys. Rev....
Reentrant anisotropic phases in a two-dimensional hole system (2006)
Manfra, M. J., Jiang, Z., Simon, S. H., Pfeiffer, L. N., West, K. W., Sergent, A. M.
Anisotropic charge transport is observed in a two-dimensional (2D) hole system in a perpendicular magnetic field at filling factors nu=7/2 and nu=11/2 for temperatures below 150mK. In stark contrast,...
Non-activated transport of strongly interacting two-dimensional holes in GaAs (2006)
Huang, Jian, Novikov, D. S., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We report on the transport measurements of two-dimensional holes in GaAs field effect transistors with record low densities down to 7*10^8 cm^{-2}. Remarkably, such a dilute system (with Fermi...
Interaction Effects and Pseudogap in Two-Dimensional Lateral Tunnel Junctions (2006)
Jiang, P., Yang, I., Kang, W., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
Tunneling characteristics of a two-dimensional lateral tunnel junction (2DLTJ) are reported. A pseudogap on the order of Coulomb energy is detected in the tunneling density of states (TDOS) when two...
Studenikin, S. A., Sachrajda, A. S., Gupta, J. A., Wasilewski, Z. R., Fedorych, O. M., Byszewski, M., ...
The frequency dependence of microwave-induced resistance oscillations (MIROs) has been studied experimentally in high-mobility electron GaAs/AlGaAs structures to explore the limits at which these...
Resistance scaling for Composite Fermions in the presence of a density gradient (2006)
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
The magnetoresistance, Rxx, at even-denominator fractional fillings, of an ultra high quality two-dimensional electron system at T ~ 35 mK is observed to be strictly linear in magnetic field, B....
Spontaneous spin polarization in quantum point contacts (2006)
Rokhinson, L. P., Pfeiffer, L. N., West, K. W.
We use spatial spin separation by a magnetic focusing technique to probe the polarization of quantum point contacts. The point contacts are fabricated from p-type GaAs/AlGaAs heterostructures. A...
Spontaneous spin polarization in quantum point contacts (2006)
Rokhinson, L. P., Pfeiffer, L. N., West, K. W.
We use spatial spin separation by a magnetic focusing technique to probe the polarization of quantum point contacts. The point contacts are fabricated from p-type GaAs/AlGaAs heterostructures. A...
Exotic electronic phases in the second Landau level (2006)
Csathy, G. A., Xia, J. S., Pan, W., Vicente, C. L., Adams, E. D., Sullivan, N. S., ...
Recent experiments have shown that two-dimensional electron systems with an externally applied magnetic field are an extremely rich ground for many-body physics. In particular, when only two of the...
Transition from Free to Interacting Composite Fermions away from $\nu$=1/3 (2006)
Gallais, Y., Kirschenmann, T. H., Dujovne, I., Hirjibehedin, C. F., Pinczuk, A., Dennis, B. S., ...
Spin excitations from a partially populated composite fermion level are studied above and below $\nu=1/3$. In the range $2/7
Spin excitations in the Fractional Quantum Hall regime at $\nu\lesssim1/3$ (2006)
Gallais, Y., Kirschenmann, T. H., Hirjibehedin, C. F., Dujovne, I., Pinczuk, A., Pfeiffer, L. N., ...
We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors $\nu\lesssim1/3$. A spin mode is observed below the Zeeman energy. The filling factor...
Spin excitations in the Fractional Quantum Hall regime at $\nu\lesssim1/3$ (2006)
Gallais, Y., Kirschenmann, T. H., Hirjibehedin, C. F., Dujovne, I., Pinczuk, A., Pfeiffer, L. N., ...
We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors $\nu\lesssim1/3$. A spin mode is observed below the Zeeman energy. The filling factor...
Transition from Free to Interacting Composite Fermions away from $\nu$=1/3 (2006)
Gallais, Y., Kirschenmann, T. H., Dujovne, I., Hirjibehedin, C. F., Pinczuk, A., Dennis, B. S., ...
Spin excitations from a partially populated composite fermion level are studied above and below $\nu=1/3$. In the range $2/7
Studenikin, S. A., Byszewski, M., Maude, D. K., Potemski, M., Sachrajda, A., Wasilewski, Z. R., ...
Microwave induced resistance oscillations (MIROs) were studied experimentally over a very wide range of frequencies ranging from similar to 20 GHz up to similar to 4 THz, and from the quasi-classical...
Multiphoton processes in microwave photoresistance of 2D electron system (2005)
Zudov, M. A., Du, R. R., Pfeiffer, L. N., West, K. W.
We extend our studies of microwave photoresistance of ultra-high mobility two-dimensional electron system (2DES) into the high-intensity, non-linear regime employing both monochromatic and...
Spin Susceptibility of a 2D Electron System in GaAs towards the Weak Interaction Region (2005)
Tan, Y. -W., Zhu, J., Stormer, H. L., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We determine the spin susceptibility $\chi$ in the weak interaction regime of a tunable, high quality, two-dimensional electron system in a GaAs/AlGaAs heterostructure. The band structure effects,...
Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Resistively-detected NMR measurements on 2D electron systems near the $\nu = 1$ quantum Hall state are reported. In contrast to recent results of Gervais \emph{et al.} [Phys. Rev. Lett. $\bf 94$,...
Negative Differential Resistance and Astability of the Wigner Solid (2005)
Csathy, G. A., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We report an unusual breakdown of the magnetically induced Wigner solid in an exceptional two-dimensional electron gas. The current-voltage characteristic is found to be hysteretic in the voltage...
Spontaneous spin polarization in quantum point contacts (2005)
Rokhinson, L. P., Pfeiffer, L. N., West, K. W.
We use spatial spin separation by a magnetic focusing technique to probe the polarization of quantum point contacts. The point contacts are fabricated from p-type GaAs/AlGaAs heterostructures. A...
Studenikin, S. A., Byszewski, M., Maude, D. K., Potemski, M., Sachrajda, A., Wasilewski, Z. R., ...
Microwave induced resistance oscillations (MIROs) were studied experimentally over a very wide range of frequencies ranging from ~20 GHz up to ~4 THz, and from the quasi-classical regime to the...
Splitting of long-wavelength modes of the fractional quantum hall liquid at ν=1/3 (2005)
Hirjibehedin, C.F., Dujovne, I., Pinczuk, A., Dennis, B.S., Pfeiffer, L.N., West, K.W.
Resonant inelastic light scattering experiments at nu=1/3 reveal a novel splitting of the long-wavelength modes in the low energy spectrum of quasiparticle excitations in the charge degree of...
Tracy, L. A., Eisenstein, J. P., Lilly, M. P., Pfeiffer, L. N., West, K. W.
We have measured the surface acoustic wave velocity shift in a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES) in a low-density regime ($
Spin-charge separation and localization in one-dimension (2005)
Auslaender, O. M., Steinberg, H., Yacoby, A., Tserkovnyak, Y., Halperin, B. I., Baldwin, K. W., ...
We report on measurements of quantum many-body modes in ballistic wires and their dependence on Coulomb interactions, obtained from tunneling between two parallel wires in a GaAs/AlGaAs...
Localization Transition in a Ballistic Quantum Wire (2005)
Steinberg, H., Auslaender, O. M., Yacoby, A., Qian, J., Fiete, G. A., Tserkovnyak, Y., ...
The many-body wave-function of an interacting one-dimensional electron system is probed, focusing on the low-density, strong interaction regime. The properties of the wave-function are determined...
Pan, W., Xia, J. S., Stormer, H. L., Tsui, D. C., Vicente, C. L., Adams, E. D., ...
We have observed quantization of the diagonal resistance, R_xx, at the edges of several quantum Hall states. Each quantized R_xx value is close to the difference between the two adjacent Hall...
Imaging Transport Resonances in the Quantum Hall Effect (2005)
Steele, G. A., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
We use a scanning capacitance probe to image transport in the quantum Hall system. Applying a DC bias voltage to the tip induces a ring-shaped incompressible strip (IS) in the 2D electron system...
Gao, X. P. A., Boebinger, G. S., Mills Jr., A. P., Ramirez, A. P., Pfeiffer, L. N., West, K. W.
We observe that an in-plane magnetic field ($B_{||}$) can induce an order of magnitude enhancement in the low temperature ($T$) resistivity ($\rho$) of metallic 2D holes in a narrow (10nm) GaAs...
Yang, C. L., Du, R. R., Pfeiffer, L. N., West, K. W.
We have studied experimentally the influence of a parallel magnetic field ($B_{//}$) on microwave-induced resistance oscillations (MIRO) and zero-resistance states (ZRS) previously discovered in a...
Spin transition in strongly correlated bilayer two-dimensional electron systems (2005)
Spielman, I. B., Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Using a combination of heat pulse and nuclear magnetic resonance techniques, we demonstrate that the phase boundary separating the interlayer phase coherent quantum Hall effect at nu(T)=1 in bilayer...
Gao, X. P. A., Boebinger, G. S., Mills Jr., A. P., Ramirez, A. P., Pfeiffer, L. N., West, K. W.
We have studied the temperature dependent phonon emission rate $P$($T$) of a strongly interacting ($r_s\geq$22) dilute 2D GaAs hole system using a standard carrier heating technique. In the still...
Manfra, M. J., Pfeiffer, L. N., West, K. W., De Picciotto, R., Baldwin, K. W.
We report on the transport properties of a high mobility two-dimensional hole system (2DHS) confined in GaAs/AlGaAs quantum wells grown molecular-beam epitaxy on the (100) surface of GaAs. The...
Nanostructures in GaAs fabricated by molecular beam epitaxy (2005)
Pfeiffer, L. N., West, K. W., Willett, R. L., Akiyama, H., Rokhinson, L. P.
We review three novel techniques whereby the highly uniform two-dimensional films produced by molecular beam epitaxy (MBE) can be further patterned into nanowires or nanostructures having quantum...
Nanostructures in GaAs fabricated by molecular beam epitaxy (2005)
Pfeiffer, L. N., West, K. W., Willett, R. L., Akiyama, H., Rokhinson, L. P.
We review three novel techniques whereby the highly uniform two-dimensional films produced by molecular beam epitaxy (MBE) can be further patterned into nanowires or nanostructures having quantum...
Tilt Induced Localization and Delocalization in the Second Landau Level (2004)
Csathy, G. A., Xia, J. S., Vicente, C. L., Adams, E. D., Sullivan, N. S., Stormer, H. L., ...
We have investigated the behavior of electronic phases of the second Landau level under tilted magnetic fields. The fractional quantum Hall liquids at $\nu=$2+1/5 and 2+4/5 and the solid phases at...
Tan, Y. -W., Zhu, J., Stormer, H. L., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We determine the density-dependent electron mass, m*, in two-dimensional (2D) electron systems of GaAs/AlGaAs heterostructures by performing detailed low-temperature Shubnikov deHaas measurements....
Evidence for Skyrmion crystallization from NMR relaxation experiments (2004)
Gervais, G., Stormer, H. L., Tsui, D. C., Kuhns, P. L., Moulton, W. G., Reyes, A. P., ...
A resistively detected NMR technique was used to probe the two-dimensional electron gas in a GaAs/AlGaAs quantum well. The spin-lattice relaxation rate $(1/T_{1})$ was extracted at near complete...
Lewis, R. M., Chen, Yong P., Engel, L. W., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We present measurements of the real diagonal microwave conductivity of the reentrant insulating quantum Hall phases in the first excited Landau level at temperatures below 50 mK. A resonance is...
Gao, Xuan P. A., Boebinger, G. S., Mills Jr., A. P., Ramirez, A. P., Pfeiffer, L. N., West, K. W.
We report the temperature($T$) and perpendicular magnetic field($B$) dependence of the Hall resistivity $\rho_{xy}(B)$ of dilute metallic two-dimensional(2D) holes in GaAs over a broad range of...
Studenikin, S. A., Potemski, M., Sachrajda, A., Hilke, M., Pfeiffer, L. N., West, K. W.
In this work we address experimentally a number of unresolved issues related to microwave induced resistance oscillations (MIRO) and the zero-resistance states observed recently on very high-mobility...
Spin Transition in Strongly Correlated Bilayer Two Dimensional Electron Systems (2004)
Spielman, I. B., Tracy, L. A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Using a combination of heat pulse and nuclear magnetic resonance techniques we demonstrate that the phase boundary separating the interlayer phase coherent quantum Hall effect at $\nu_T = 1$ in...
Oscillatory and Vanishing Resistance States in Microwave Irradiated 2D Electron Systems (2004)
Du, R. R., Zudov, M. A., Yang, C. L., Yuan, Z. Q., Pfeiffer, L. N., West, K. W.
Giant-amplitude oscillations in dc magnetoresistance of a high-mobility two-dimensional electron system can be induced by millimeterwave irradiations, leading to zero-resistance states at the...
Pan, W., Csathy, G. A., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We have observed in a low density two-dimensional hole system (2DHS) of extremely high quality (with hole density p=1.6x10^{10} cm^{-2} and mobility \mu=0.8x10^6 cm^2/Vs) that, as the 2DHS is...
Magnetic Field Induced Insulating Phases at Large $r_s$ (2004)
Csáthy, G. A., Noh, Hwayong, Tsui, D. C., Pfeiffer, L. N., West, K. W.
Exploring a backgated low density two-dimensional hole sample in the large $r_s$ regime we found a surprisingly rich phase diagram. At the highest densities, beside the $\nu=1/3$, 2/3, and 2/5...
Spielman, I. B., Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Tunneling and Coulomb drag are sensitive probes of spontaneous interlayer phase coherence in bilayer two-dimensional electron systems at total Landau level filling factor nu(T)=1. We find that the...
Quantum Hall line junction with impurities as a multi-slit Luttinger liquid interferometer (2004)
Yang, I., Kang, W., Pfeiffer, L. N., Baldwin, K. W., West, K. W., Kim, Eun-Ah, ...
We report on quantum interference between a pair of counterpropagating quantum Hall edge states that are separated by a high quality tunnel barrier. Observed Aharonov-Bohm oscillations are analyzed...
Chen, Yong P., Wang, Z. H., Lewis, R. M., Ye, P. D., Engel, L. W., Tsui, D. C., ...
We have measured high frequency magnetotransport of a high quality two-dimensional electron system (2DES) near the reentrant insulating phase (RIP) at Landau fillings ($\nu$) between 1/5 and 2/9. The...
Evidence for Two Different Solid Phases of Two Dimensional Electrons in High Magnetic Fields (2004)
Chen, Yong P., Lewis, R. M., Engel, L. W., Tsui, D. C., Ye, P. D., Wang, Z. H., ...
We have performed RF spectroscopy on very high quality two dimensional electron systems in the high magnetic field insulating phase, usually associated with a Wigner solid (WS) pinned by disorder. We...
Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
At total Landau level filling factor nutot = 1 a double-layer two-dimensional electron system with small interlayer separation supports a collective state possessing spontaneous interlayer phase...
Splitting of Long-Wavelength Modes of the Fractional Quantum Hall Liquid at $\nu=1/3$ (2004)
Hirjibehedin, C. F., Dujovne, Irene, Pinczuk, A., Dennis, B. S., Pfeiffer, L. N., West, K. W.
Resonant inelastic light scattering experiments at $\nu=1/3$ reveal a novel splitting of the long wavelength modes in the low energy spectrum of quasiparticle excitations in the charge degree of...
Xia, J. S., Pan, W., Vincente, C. L., Adams, E. D., Sullivan, N. S., Stormer, H. L., ...
At a very low temperature of 9mK, electrons in the 2nd Landau level of an extremely high mobility two-dimensional electron system exhibit a very complex electronic behavior. With varying filling...
2D Metal-Insulator transition as a percolation transition (2004)
Sarma, S. Das, Lilly, M. P., Hwang, E. H., Pfeiffer, L. N., West, K. W., Reno, J. L.
By carefully analyzing the low temperature density dependence of 2D conductivity in undoped high mobility n-GaAs heterostructures, we conclude that the 2D metal-insulator transition in this system is...
Spielman, I. B., Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Tunneling and Coulomb drag are sensitive probes of spontaneous interlayer phase coherence in bilayer two-dimensional electron systems at total Landau level filling factor $\nu_T = 1$. We find that...
Studenikin, S. A., Potemski, M., Sachrajda, A., Hilke, M., Pfeiffer, L. N., West, K. W.
We have performed simultaneous measurements of microwave absorption/reflection and magneto-transport characteristics of a high mobility two-dimensional electrons in GaAs/AlGaAs heterostructure in...
Spin separation in cyclotron motion (2004)
Rokhinson, L. P., Larkina, V., Lyanda-Geller, Y. B., Pfeiffer, L. N., West, K. W.
Charged carriers with different spin states are spatially separated in a two-dimensional hole gas. Due to strong spin-orbit interaction holes at the Fermi energy have different momenta for two...
Yasin, C. E., Sobey, T. L., Micolich, A. P., Hamilton, A. R., Simmons, M. Y., Pfeiffer, L. N., ...
We present a systematic study of the corrections to both the longitudinal conductivity and Hall resistivity due to electron-electron interactions in high quality GaAs systems using the recent theory...
Csathy, G. A., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We have measured the magnetoresistance of a very low density and an extremely high quality two-dimensional hole system. With increasing magnetic field applied perpendicularly to the sample we observe...
Gervais, G., Engel, L. W., Stormer, H. L., Tsui, D. C., Baldwin, K. W., West, K. W., ...
Magnetotransport measurements were performed in a ultra-high mobility GaAs/AlGaAs quantum well of density $\sim 3.0 \times 10^{11}$ $cm^{-2}$. The temperature dependence of the magnetoresistance...
Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
At total Landau level filling factor $\nu_{tot}=1$ a double layer two-dimensional electron system with small interlayer separation supports a collective state possessing spontaneous interlayer phase...
Lewis, R. M., Chen, Yong, Engel, L. W., Tsui, D. C., Ye, P. D., Pfeiffer, L. N., ...
For filling factors $\nu$ in the range between 4.16 and 4.28, we simultaneously detect {\it two} resonances in the real diagonal microwave conductivity of a two--dimensional electron system (2DES) at...
Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
In half-filled high Landau levels, two-dimensional electron systems possess collective phases which exhibit a strongly anisotropic resistivity tensor. A weak, but as yet unknown, rotational...
Cascade of Quantum Phase Transitions in Tunnel-Coupled Edge States (2003)
Yang, I., Kang, W., Baldwin, K. W., Pfeiffer, L. N., West, K. W.
We report on the cascade of quantum phase transitions exhibited by tunnel-coupled edge states across a quantum Hall line junction. We identify a series of quantum critical points between successive...
Hirjibehedin, C.F., Pinczuk, A., Dennis, B.S., Pfeiffer, L.N., West, K.W.
New low-lying excitations are observed by inelastic light scattering at filling factors ν=p/(ϕp±1) of the fractional quantum Hall regime with ϕ=4. Coexisting with these modes throughout the range...
Ultrafast Dynamic Control of Spin and Charge Density Oscillations in a GaAs Quantum Well (2003)
Bao, J. M., Pfeiffer, L. N., West, K. W., Merlin, R.
We use subpicosecond laser pulses to generate and monitor in real time collective oscillations of electrons in a modulation-doped GaAs quantum well. The observed frequencies match those of...
Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
In half-filled high Landau levels, two-dimensional electron systems possess collective phases which exhibit a strongly anisotropic resistivity tensor. A weak, but as yet unknown, rotational...
Light Scattering by Low Lying Quasiparticle Excitations in the Fractional Quantum Hall Regime (2003)
Hirjibehedin, C. F., Dujovne, Irene, Pinczuk, A., Dennis, B. S., Pfeiffer, L. N., West, K. W.
Low lying excitations of electron liquids in the fractional quantum Hall (FQH) regime are studied by resonant inelastic light scattering methods. We present here results from charge and spin...
Willett, R. L., Pfeiffer, L. N., West, K. W.
We report experimental results of low temperature magnetotransport in high mobility 2D electron systems exposed to radiation up to 20GHz frequency using a simple dipole configuration....
Fermi liquid behavior of metallic 2D holes at high temperatures (2003)
Gao, Xuan P. A., Mills Jr., A. P., Ramirez, A. P., Pfeiffer, L. N., West, K. W.
The resistivity $\rho$ of high mobility dilute 2D holes in GaAs exhibits a peak at a certain temperature $T^*$ in zero magnetic field($B$=0). In the $T>T^*$ regime where d$\rho$/d$T$0) for $T
Wigner crystalization about $\nu$=3 (2003)
Lewis, R. M., Chen, Yong, Engel, L. W., Tsui, D. C., Ye, P. D., Pfeiffer, L. N., ...
We measure a resonance in the frequency dependence of the real diagonal conductivity, Re[$\sigma_{xx}$], near integer filling factor, $\nu=3$. This resonance depends strongly on $\nu$, with peak...
Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Measurements revealing anomalously large frictional drag at the transition between the weakly and strongly coupled regimes of a bilayer two-dimensional electron system at total Landau level filling...
Experiments on the Fermi to Tomonaga-Luttinger liquid transition in quasi-1D systems (2003)
Hilke, M., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We present experimental results on the tunneling into the edge of a two dimensional electron gas (2DEG) obtained with GaAs/AlGaAs cleaved edge overgrown structures. The electronic properties of the...
Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Recent magnetotransport experiments on high mobility two-dimensional electron systems have revealed many-body electron states unique to high Landau levels. Among these are reentrant integer quantum...
Dujovne, I., Hirjibehedin, C. F., Pinczuk, A., Kang, Moonsoo, Dennis, B. S., Pfeiffer, L. N., ...
Resonant inelastic light scattering experiments access the low lying excitations of electron liquids in the fractional quantum Hall regime in the range $2/5 \geq \nu \geq 1/3$. Modes associated with...
Hirjibehedin, C. F., Pinczuk, A., Dennis, B. S., Pfeiffer, L. N., West, K. W.
New low-lying excitations are observed by inelastic light scattering at filling factors $\nu=p/(\phi p \pm 1)$ of the fractional quantum Hall regime with $\phi=4$. Coexisting with these modes...
Real-time detection of electron tunnelling in a quantum dot (2003)
Wei Lu, Zhongqing Ji, Loren Pfeiffer, K. W. West, A. J. Rimberg
Observation of Apparently Zero-Conductance States in Corbino Samples (2003)
Yang, C. L., Zudov, M. A., Knuuttila, T. A., Du, R. R., Pfeiffer, L. N., West, K. W.
Using Corbino samples we have observed oscillatory conductance in a high-mobility two-dimensional electron system subjected to crossed microwave and magnetic fields. On the strongest of the...
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
At low Landau level filling of a two-dimensional electron system, typically associated with the formation of an electron crystal, we observe local minima in Rxx at filling factors nu=2/11, 3/17,...
Fractional Quantum Hall Effect of Composite Fermions (2003)
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
In a GaAs/AlGaAs quantum well of electron density 1x10^{11} cm^{-2} we observe a fractional quantum Hall effect (FQHE) at filling factors nu=4/11, and 5/13, and weaker states at nu=6/17, 4/13, 5/17...
AFM local oxidation nanopatterning of a high mobility shallow 2D hole gas (2003)
Rokhinson, L. P., Tsui, D. C., Pfeiffer, L. N., West, K. W.
Recently developed AFM local anodic oxidation (LAO) technique offers a convenient way of patterning nanodevices, but imposes even more stringent requirements on the underlying quantum well structure....
Yang, I., Kang, W., Hannahs, S. T., Pfeiffer, L. N., West, K. W.
We have observed an anomalous shift of the high field reentrant insulating phases in a two-dimensional electron system (2DES) tightly confined within a narrow GaAs/AlGaAs quantum well. Instead of the...
Resistivity of dilute 2D electrons in an undoped GaAs heterostructure (2003)
Lilly, M. P., Reno, J. L., Simmons, J. A., Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., ...
We report resistivity measurements from 0.03 to 10 K in a dilute high mobility 2D electron system. Using an undoped GaAs/AlGaAs heterojunction in a gated field-effect transistor geometry, a wide...
Microwave Resonance of 2D Wigner Crystal around integer Landau fillings (2003)
Chen, Yong P., Lewis, R. M., Engel, L. W., Tsui, D. C., Ye, P. D., Pfeiffer, L. N., ...
We have observed a resonance in the real part of the finite frequency diagonal conductivity using microwave absorption measurements in high quality 2D electron systems near {\em integer fillings}....
Noh, Hwayong, Lilly, M. P., Tsui, D. C., Simmons, J. A., Pfeiffer, L. N., West, K. W
The conductivity of extremely high mobility dilute two-dimensional holes in GaAs changes linearly with temperature in the insulating side of the metal-insulator transition. Hopping conduction,...
Spin Susceptibility of an Ultra-Low Density Two Dimensional Electron System (2003)
Zhu, J., Stormer, H. L., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We determine the spin susceptibility in a two dimensional electron system in GaAs/AlGaAs over a wide range of low densities from 2$\times10^{9}$cm$^{-2}$ to 4$\times10^{10}$cm$^{-2}$. Our data can be...
Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Frictional drag measurements revealing anomalously large dissipation at the transition between the weakly- and strongly-coupled regimes of a bilayer two-dimensional electron system at total Landau...
Density dependent spin polarisation in ultra-low disorder quantum wires (2002)
Reilly, D. J., Buehler, T. M., O'Brien, J. L., Hamilton, A. R., Dzurak, A. S., Clark, R. G., ...
There is controversy as to whether a one-dimensional (1D) electron gas can spin polarize in the absence of a magnetic field. Together with a simple model, we present conductance measurements on...
Resistivity of dilute 2D electrons in an undoped GaAs heterostructure (2002)
Lilly, M. P., Reno, J. L., Simmons, J. A., Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., ...
We report resistivity measurements from 0.03 K to 10 K in a dilute high mobility 2D electron system. Using an undoped GaAs/AlGaAs heterojunction in a gated field-effect transistor geometry, a wide...
Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Recent magnetotransport experiments on high mobility two-dimensional electron systems have revealed many-body electron states unique to high Landau levels. Among these are re-entrant integer quantum...
Evidence for a New Dissipationless Regime in 2D Electronic Transport (2002)
Zudov, M. A., Du, R. R., Pfeiffer, L. N., West, K. W.
In an ultra-clean 2D electron system (2DES) subjected to crossed millimeterwave (30--150 GHz) and weak (B < 2 kG) magnetic fields, a series of apparently dissipationless states emerges as the system...
Evidence for 2k_F Electron-Electron Scattering Processes in Coulomb Drag (2002)
Kellogg, M., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Measurements and calculations of Coulomb drag between two low density, closely spaced, two-dimensional electron systems are reported. The experimentally measured drag exceeds that calculated in the...
Interaction Corrections to Two-Dimensional Hole Transport in Large $r_{s}$ Limit (2002)
Noh, Hwayong, Lilly, M. P., Tsui, D. C., Simmons, J. A., Hwang, E. H., Sarma, S. Das, ...
The metallic conductivity of dilute two-dimensional holes in a GaAs HIGFET (Heterojunction Insulated-Gate Field-Effect Transistor) with extremely high mobility and large $r_{s}$ is found to have a...
Cooper, K. B., Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The recently discovered anisotropy of the longitudinal resistance of two-dimensional electrons near half filling of high Landau levels is found to persist to much higher temperatures T when a large...
Microwave resonances of the bubble phases in 1/4 and 3/4 filled higher Landau levels (2002)
Lewis, R. M., Ye, P. D., Engel, L. W., Tsui, D. C., Pfeiffer, L. N., West, K. W.
We have measured the diagonal conductivity in the microwave regime of an ultrahigh mobility two dimensional electron system. We find a sharp resonance in Re[sigma_{xx}] versus frequency when nu > 4...
Universal behaviour in the floating up of quantum Hall extended states as B -> 0 (2002)
Yasin, C. E., Simmons, M. Y., Hamilton, A. R., Lumpkin, N. E., Clark, R. G., Pfeiffer, L. N., ...
We investigate the relationship between the quantum Hall extended states and the apparent B=0 `metal'-insulator transition in extremely low density, high quality two-dimensional n-GaAs systems...
Observation of Quantized Hall Drag in a Strongly Correlated Bilayer Electron System (2002)
Kellogg, M., Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The frictional drag between parallel two-dimensional electron systems has been measured in a regime of strong interlayer correlations. When the bilayer system enters the excitonic quantized Hall...
Density Induced Interchange of Anisotropy Axes at Half-Filled High Landau Levels (2002)
Zhu, J., Pan, W., Stormer, H. L., Pfeiffer, L. N., West, K. W.
We observe density induced 90$^{\circ}$ rotations of the anisotropy axes in transport measurements at half-filled high Landau levels in the two dimensional electron system, where stripe states are...
Cooper, K. B., Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The recently discovered anisotropy of the longitudinal resistance of two-dimensional electrons near half filling of high Landau levels is found to persist to much higher temperatures T when a large...
Density dependent spin polarisation in ultra low-disorder quantum wires (2002)
Reilly, D. J., Buehler, T. M., O'Brien, J. L., Hamilton, A. R., Dzurak, A. S., Clark, R. G., ...
There is controversy as to whether a one-dimensional (1D) electron gas can spin polarise in the absence of a magnetic field. Together with a simple model, we present conductance measurements on ultra...
Insulating and Fractional Quantum Hall States in the First Excited Landau Level (2002)
Eisenstein, J. P., Cooper, K. B., Pfeiffer, L. N., West, K. W.
The observation of new insulating phases of two-dimensional electrons in the first excited Landau level is reported. These states, which are manifested as reentrant integer quantized Hall effects,...
An all-cryogenic THz transmission spectrometer (2002)
Burke, P. J., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
This article describes a THz transmission spectrometer for the spectral range of 2–65 cm–1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8 cm–1 (50 GHz) where the source, sample,...
Density dependent spin polarisation in ultra-low disorder quantum wires (2002)
Reilly, D. J., Buehler, T. M., O'Brien, J. L., Hamilton, A. R., Dzurak, A. S., Clark, R. G., ...
There is controversy as to whether a one-dimensional (1D) electron gas can spin polarize in the absence of a magnetic field. Together with a simple model, we present conductance measurements on...
Density-Dependent Spin Polarization in Ultra-Low -Disorder Quantum Wires (2002)
Reilly, D.J., Buehler, T.M., O'Brien, J. L., Hamilton, A. R., Dzurak, A, Clark, R., ...
Density dependent spin polarisation in ultra-low disorder quantum wires (2002)
Reilly, D. J., Buehler, T. M., O'Brien, J. L., Hamilton, A. R., Dzurak, A. S., Clark, R. G., ...
There is controversy as to whether a one-dimensional (1D) electron gas can spin polarize in the absence of a magnetic field. Together with a simple model, we present conductance measurements on...
Density-Dependent Spin Polarization in Ultra-Low -Disorder Quantum Wires (2002)
Reilly, D.J., Buehler, T.M., O'Brien, J. L., Hamilton, A. R., Dzurak, A, Clark, R., ...
Insulating and Fractional Quantum Hall States in the N=1 Landau Level (2001)
Eisenstein, J. P., Cooper, K. B., Pfeiffer, L. N., West, K. W.
The observation of new insulating phases of two-dimensional electrons in the first excited Landau level is reported. These states, which are manifested as re-entrant integer quantized Hall effects,...
Current Path Properties of the Transport Anisotropy at Filling Factor 9/2 (2001)
Willett, R. L., West, K. W., Pfeiffer, L. N.
To establish the presence and orientation of the proposed striped phase in ultra-high mobility 2D electron systems at filling factor 9/2, current path transport properties are determined by varying...
Experimental Demonstration of Fermi Surface Effects at Filling Factor 5/2 (2001)
Willett, R. L., West, K. W., Pfeiffer, L. N.
Using small wavelength surface acoustic waves (SAW) on ultra-high mobility heterostructures, Fermi surface properties are detected at 5/2 filling factor at temperatures higher than those at which the...
Observation of Quantized Hall Drag in a Strongly Correlated Bilayer Electron System (2001)
Kellogg, M., Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The frictional drag between parallel two-dimensional electron systems has been measured in a regime of strong interlayer correlations. When the bilayer system enters the excitonic quantized Hall...
Effect of Nyquist Noise on the Nyquist Dephasing Rate in 2d Electron Systems (2001)
Burke, P. J., Pfeiffer, L. N., West, K. W.
We measure the effect of externally applied broadband Nyquist noise on the intrinsic Nyquist dephasing rate of electrons in a two-dimensional electron gas at low temperatures. Within the measurement...
An All-Cryogenic THz Transmission Spectrometer (2001)
Burke, P. J., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
This paper describes a THz transmission spectrometer for the spectral range of 2-65 cm^-1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8 cm^-1 (50 GHz) where the source, sample, and...
Observation of a linearly dispersing collective mode in a quantum Hall ferromagnet (2001)
Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Double-layer two-dimensional electron systems can exhibit a fascinating collective phase believed to display both quantum ferromagnetism and excitonic superfluidity. This unusual phase has recently...
Fermi liquid to Luttinger liquid transition at the edge of a two-dimensional electron gas (2001)
Hilke, M., Tsui, D. C., Grayson, M., Pfeiffer, L. N., West, K. W.
We present experimental results on the tunneling into the edge of a two dimensional electron gas (2DEG) obtained with a GaAs/AlGaAs cleaved edge overgrown structure in a strong perpendicular magnetic...
An Investigation of Orientational Symmetry-Breaking Mechanisms in High Landau Levels (2001)
Cooper, K. B., Lilly, M. P., Eisenstein, J. P., Jungwirth, T., Pfeiffer, L. N., West, K. W.
The principal axes of the recently discovered anisotropic phases of 2D electron systems at high Landau level occupancy are consistently oriented relative to the crystal axes of the host...
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We study the \nu=5/2 even-denominator fractional quantum Hall effect (FQHE) over a wide range of magnetic (B) field in a heterojunction insulated gate field-effect transistor (HIGFET). The electron...
Highly Anisotropic Transport in the Integer Quantum Hall Effect (2001)
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
At very large tilt of the magnetic (B) field with respect to the plane of a two-dimensional electron system the transport in the integer quantum Hall regime at $\nu$ = 4, 6, and 8 becomes strongly...
Suppression of weak localization effects in low-density metallic 2D holes (2001)
Mills Jr., A. P., Ramirez, A. P., Gao, X. P. A., Pfeiffer, L. N., West, K. W., Simon, S. H.
We have measured the conductivity in a gated high-mobility GaAs two dimensional hole sample with densities in the range (7-17)x10^9 cm^-2 and at hole temperatures down to 5x10^-3 E_F. We measure the...
Observation of a Linearly Dispersing Collective Mode in a Quantum Hall Ferromagnet (2001)
Eisenstein, J. P., Pfeiffer, L. N., Spielman, I. B., West, K. W.
Fermi Liquid to Luttinger Liquid Transition at the Edge of a Two-Dimensional Electron Gas (2001)
Grayson, M., Hilke, M., Pfeiffer, L. N., Tsui, D. C., West, K. W.
Plateau Behavior in the Chiral Luttinger Liquid Exponent (2001)
Chang, A. M., Chi, C. C., Pfeiffer, L. N., West, K. W., Wu, M. K.
Observation of Multiple Magnetorotons in the Fractional Quantum Hall Effect (2001)
Dennis, B. S., Kang, Moonsoo, Pfeiffer, L. N., Pinczuk, A., West, K. W.
Resonant Tunneling into a Biased Fractional Quantum Hall Edge (2001)
Chang, A. M., Grayson, M., Pfeiffer, L. N., Tsui, D. C., West, K. W.
Observation of a Linearly Dispersing Collective Mode in a Quantum Hall Ferromagnet (2000)
Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Double layer two-dimensional electron systems can exhibit a fascinating collective phase believed to exhibit both quantum ferromagnetism and excitonic superfluidity. This unusual phase has recently...
Spectroscopic Evidence for the Localization of Skyrmions near Nu=1 as T->0 (2000)
Khandelwal, P., Dementyev, A. E., Kuzma, N. N., Barrett, S. E., Pfeiffer, L. N., West, K. W.
Optically pumped nuclear magnetic resonance measurements of Ga-71 spectra were carried out in an n-doped GaAs/Al0.1Ga0.9As multiple quantum well sample near the integer quantum Hall ground state...
Willett, R. L., Hsu, J. W. P., Natelson, D., West, K. W., Pfeiffer, L. N.
Surface morphology of high mobility heterostructures is examined and correlated with d.c. transport. {\it All} samples examined show evidence of lines in the [1$\bar{1}$0] direction with roughness...
Geometry dependent dephasing in small metallic wires (2000)
Natelson, D., Willett, R. L., West, K. W., Pfeiffer, L. N.
Temperature dependent weak localization is measured in metallic nanowires in a previously unexplored size regime down to width $w=5$ nm. The dephasing time, $\tau_{\phi}$, shows a low temperature $T$...
Resonantly Enhanced Tunneling in a Double Layer Quantum Hall Ferromagnet (2000)
Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total Landau level filling νT = 1 the tunnel spectrum...
Imaging of localized electronic states in the quantum Hall regime (2000)
N. B. Zhitenev, T. A. Fulton, A. Yacoby, H. F. Hess, L. N. Pfeiffer, K. W. West
Reorientation of Anisotropy in a Square Well Quantum Hall Sample (2000)
Pan, W., Jungwirth, T., Stormer, H. L., Tsui, D. C., MacDonald, A. H., Girvin, S. M., ...
We have measured magnetotransport at half-filled high Landau levels in a quantum well with two occupied electric subbands. We find resistivities that are {\em isotropic} in perpendicular magnetic...
New collective states of 2D electrons in high Landau levels (2000)
Eisenstein, J. P, Lilly, M. P., Cooper, K. B., Pfeiffer, L. N., West, K. W.
A brief summary of the emerging evidence for a new class of collective states of two-dimensional electrons in partially occupied excited Landau levels is presented. Among the most dramatic phenomena...
Evidence for a Goldstone Mode in a Double Layer Quantum Hall System (2000)
Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total Landau level filling $\nu_T=1$ the tunnel spectrum...
High frequency conductivity of the high-mobility two-dimensional electron gas (2000)
Burke, P. J., Spielman, I. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We measure the real and imaginary conductivity sigma(k = 0,omega) of a high-mobility two-dimensional electron gas (2DEG) system at frequencies below and above the momentum scattering rate. The...
Localization in Artificial Disorder - Two Coupled Quantum Dots (2000)
Brodsky, M., Zhitenev, N. B., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
Using Single Electron Capacitance Spectroscopy, we study electron additions in quantum dots containing two potential minima separated by a shallow barrier. Analysis of addition spectra in magnetic...
Many-body spin related phenomena in ultra-low-disorder quantum wires (2000)
Reilly, D. J., Facer, G. R., Dzurak, A. S., Kane, B. E., Clark, R. G., Stiles, P. J., ...
Zero length quantum wires (or point contacts) exhibit unexplained conductance structure close to 0.7 X 2e^2/h in the absence of an applied magnetic field. We have studied the density- and...
Tunnelling between the edges of two lateral quantum Hall systems (2000)
W. Kang, H. L. Stormer, L. N. Pfeiffer, K. W. Baldwin, K. W. West
The Localization-Delocalization Transition in Quantum Dots (1999)
Zhitenev, N. B., Brodsky, M., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
Single-electron capacitance spectroscopy precisely measures the energies required to add individual electrons to a quantum dot. The spatial extent of electronic wavefunctions is probed by...
Inelastic Light Scattering by Gap Excitations of Fractional Quantum Hall States at 1/3 (1999)
Kang, Moonsoo, Pinczuk, A., Dennis, B. S., Eriksson, M. A., Pfeiffer, L. N., West, K. W.
We report observations of collective gap excitations of the fractional quantum Hall (FQH) states at filling factors \nu=p/(2p+1) (p=integer), for 1/3
Cooper, K. B., Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The intriguing re-entrant integer quantized Hall states recently discovered in high Landau levels of high-mobility 2D electron systems are found to exhibit extremely nonlinear transport. At small...
Tunneling between the Edges of Two Lateral Quantum Hall Systems (1999)
Kang, W., Stormer, H. L., Baldwin, K. W., Pfeiffer, L. N., West, K. W.
The edge of a two-dimensional electron system (2DES) in a magnetic field consists of one-dimensional (1D) edge-channels that arise from the confining electric field at the edge of the...
Effective Mass of the Four Flux Composite Fermion at $\nu = 1/4$ (1999)
Pan, W., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We have measured the effective mass ($m^*$) of the four flux composite fermion at Landau level filling factor $\nu = 1/4$ ($^4$CF), using the activation energy gaps at the fractional quantum Hall...
Enhancement of Coulomb drag away from half filled Landau levels (1999)
Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Coulomb drag between two parallel two dimensional electron gases has been measured at high magnetic fields in samples with two different layer spacings. As the layer filling factor deviates from...
New Physics in High Landau Levels (1999)
Eisenstein, J. P., Lilly, M. P., Cooper, K. B., Pfeiffer, L. N., West, K. W.
Recent magneto-transport experiments on ultra-high mobility 2D electron systems in GaAs/AlGaAs heterostructures have revealed the existence of whole new classes of correlated many-electron states in...
Experimental Evidence for Resonant-Tunneling in a Luttinger-Liquid (1999)
Auslaender, O. M., Yacoby, A., De Picciotto, R., Baldwin, K. W., Pfeiffer, L. N., West, K. W.
We have measured the low temperature conductance of a one-dimensional island embedded in a single mode quantum wire. The quantum wire is fabricated using the cleaved edge overgrowth technique and the...
Hysteresis and Spikes in the Quantum Hall Effect (1999)
Zhu, J., Stormer, H. L., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We observe sharp peaks and strong hysteresis in the electronic transport of a two-dimensional electron gas (2DEG) in the region of the integral quantum Hall effect. The peaks decay on time scales...
Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We report the observation of an acute sensitivity of the anisotropic longitudinal resistivity of two-dimensional electron systems in half-filled high Landau levels to the magnitude and orientation of...
Missing 2k_F Response for Composite Fermions in Phonon Drag (1999)
Zelakiewicz, S., Noh, H., Gramila, T. J., Pfeiffer, L. N., West, K. W.
The response of composite Fermions to large wavevector scattering has been studied through phonon drag measurements. While the response retains qualitative features of the electron system at zero...
Pan, W., Xia, J. -S., Shvarts, V., Adams, E. D., Stormer, H. L., Tsui, D. C., ...
We report ultra-low temperature experiments on the obscure fractional quantum Hall effect (FQHE) at Landau level filling factor $\nu$=5/2 in a very high mobility specimen of $\mu=1.7 \times 10^7$...
Cooper, K. B., Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
The intriguing re-entrant integer quantized Hall states recently discovered in high Landau levels of high-mobility 2D electron systems are found to exhibit extremely non-linear transport. At small...
Ultraslow Electron Spin Dynamics in GaAs Quantum Wells Probed by Optically Pumped NMR (1999)
Kuzma, N. N., Khandelwal, P., Barrett, S. E., Pfeiffer, L. N., West, K. W.
Optically pumped nuclear magnetic resonance (OPNMR) measurements were performed in two different electron-doped multiple quantum well samples near the fractional quantum Hall effect ground state...
Dementyev, A. E., Kuzma, N. N., Khandelwal, P., Barrett, S. E., Pfeiffer, L. N., West, K. W.
The Knight shift and the nuclear spin-lattice relaxation rate 1/T1 of Ga-71 nuclei are measured in GaAs quantum wells at Landau level filling factor nu = 1/2 using optically pumped NMR. The...
Tunneling into Ferromagnetic Quantum Hall States: Observation of a Spin Bottleneck (1999)
Chan, H. B., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
We explore the characteristics of equilibrium tunneling of electrons from a 3D electrode into a high mobility 2D electron system. For most 2D Landau level filling factors, we find that tunneling can...
Nonmonotonic Temperature-dependent Resistance in Low Density 2D Hole Gases (1999)
Mills, A. P., Jr., Ramirez, A. P., Pfeiffer, L. N., West, K. W.
The low temperature longitudinal resistance-per-square Rxx(T) in ungated GaAs/AlGaAs quantum wells of high peak hole mobility 1.7x10^6 cm^2/Vs is metallic for 2D hole density p as low as 3.8x10^9...
Phonon mediated drag in double layer two dimensional electron systems (1999)
Noh, H., Zelakiewicz, S., Gramila, T. J., Pfeiffer, L. N., West, K. W.
Experiments studying phonon mediated drag in the double layer two dimensional electron gas system are reported. Detailed measurements of the dependence of drag on temperature, layer spacing, density...
Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We report the observation of an acute sensitivity of the anisotropic longitudinal resistivity of two-dimensional electron systems in half-filled high Landau levels to the magnitude and orientation of...
Pan, W., Du, R. R., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., ...
We have investigated the influence of an increasing in-plane magnetic field on the states at half-filling of Landau levels ($\nu$ = 11/2, 9/2, 7/2, and 5/2) of a two-dimensional electron system. In...
Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We recently reported [PRL 82, 394 (1999)] large transport anisotropies in a two-dimensional electron gas in high Landau levels. These observations were made utilizing both square and Hall bar sample...
Evidence for an anisotropic state of two-dimensional electrons in high Landau levels (1999)
Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Magnetotransport experiments on high mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures have revealed striking anomalies near half filling of several spin-resolved, yet highly...
Heron, R. J., Lewis, R. A., Kane, B. E., Facer, G. R., Clark, R. G., Dzurak, A. S., ...
We report on the far-infrared photoresponse of a quantum point contact device fabricated on a top-gated GaAs/AlGaAs heterostructure. The top-gated architecture avoids the disorder built into...
Heron, R. J., Lewis, R. A., Kane, B. E., Facer, G. R., Clark, R. G., Dzurak, A. S., ...
We report on the far-infrared photoresponse of a quantum point contact device fabricated on a top-gated GaAs/AlGaAs heterostructure. The top-gated architecture avoids the disorder built into...
Heron, R. J., Lewis, R. A., Kane, B. E., Facer, G. R., Clark, R. G., Dzurak, A. S., ...
We report on the far-infrared photoresponse of a quantum point contact device fabricated on a top-gated GaAs/AlGaAs heterostructure. The top-gated architecture avoids the disorder built into...
Heron, R. J., Lewis, R. A., Kane, B. E., Facer, G. R., Clark, R. G., Dzurak, A. S., ...
We report on the far-infrared photoresponse of a quantum point contact device fabricated on a top-gated GaAs/AlGaAs heterostructure. The top-gated architecture avoids the disorder built into...
Strongly Anisotropic Transport in Higher Two-Dimensional Landau Levels (1998)
Du, R. R., Tsui, D. C., Stormer, H. L., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
Low-temperature, electronic transport in Landau levels N>1 of a two-dimensional electron system is strongly anisotropic. At half-filling of either spin level of each such Landau level the...
Observation of Collective Excitations of the Dilute 2D Electron System (1998)
Eriksson, M. A., Pinczuk, A., Dennis, B. S., Simon, S. H., Pfeiffer, L. N., West, K. W.
We report inelastic light scattering measurements of dispersive spin and charge density excitations in dilute 2D electron systems reaching densities less than 10^{10} cm^{-2}. In the quantum Hall...
Effective Mass and g-Factor of Four Flux Quanta Composite Fermions (1998)
Yeh, A. S., Stormer, H. L., Tsui, D. C., Pfeiffer, L. N., Baldwin, K. W., West, K. W.
We investigate the properties of composite fermions with four attached flux quanta through tilted field experiments near Landau level filling factor nu = 3/4. The observed collapse of fractional...
Negative Electron Drag and Hole-Like behavior in the Integer Quantum Hall Regime (1998)
Feng, X. G., Zelakiewicz, S., Noh, H., Ragucci, T. J., Gramila, T. J., Pfeiffer, L. N., ...
Electron drag between two two-dimensional electron gases in magnetic fields has been observed with a polarity opposite that for zero field. This negative drag requires that the electrons have a...
Noh, H., Zelakiewicz, S., Feng, X. G., Gramila, T. J., Pfeiffer, L. N., West, K. W.
Electron drag measurements of electron-electron scattering rates performed close to the Fermi temperature are reported. While evidence of an enhancement due to plasmons, as was recently predicted [K....
Evidence for an Anisotropic State of Two-Dimensional Electrons in High Landau Levels (1998)
Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Magneto-transport experiments on high mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures have revealed striking anomalies near half-filling of several spin-resolved, yet highly...
Koltonyuk, M., Berman, D., Zhitenev, N. B., Ashoori, R. C., Pfeiffer, N., West, K. W.
We have incorporated an aluminum single electron transistor (SET) directly on top of a vertical quantum dot, enabling the use of the SET as an electrometer that is extremely responsive to the motion...
Ballistic electron transport exceeding 160 microns in an undoped GaAs/AlGaAs FET (1998)
Facer, G. R., Kane, B. E., Dzurak, A. S., Heron, R. J., Lumpkin, N. E., Clark, R. G., ...
We report measurements of GaAs/AlGaAs undoped field-effect transistors in which two-dimensional electron gases (2DEGs) of exceptional quality and versatility are induced without modulation doping....
Coulomb drag in the extreme quantum limit (1998)
Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Coulomb drag resulting from interlayer electron-electron scattering in double layer 2D electron systems in a high magnetic field has been measured. Within the lowest Landau level the observed drag...
Khandelwal, P., Kuzma, N. N., Barrett, S. E., Pfeiffer, L. N., West, K. W.
The Knight shift of Ga-71 nuclei is measured in two different electron-doped multiple quantum well samples using optically pumped NMR. These data are the first direct measurements of the electron...
Coulomb Drag in the Extreme Quantum Limit (1997)
Lilly, M. P., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Coulomb drag resulting from interlayer electron-electron scattering in double layer 2D electron systems at high magnetic field has been measured. Within the lowest Landau level the observed drag...
Periodic and Aperiodic Bunching in the Addition Spectra of Quantum Dot (1997)
Zhitenev, N. B., Ashoori, R. C., Pfeiffer, L. N., West, K. W.
We study electron addition spectra of quantum dots in a broad range of electron occupancies starting from the first electron. Spectra for dots containing
Evidence for Skyrmions and single spin flips in the integer quantized Hall effect (1995)
Schmeller, A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We have employed tilted-field magnetotransport measurements of the energy gap for the odd-integer quantized Hall states at Landau level filling factors ν=1, 3, and 5 to determine the spin of...
Evidence for Skyrmions and Single Spin Flips in the Integer Quantized Hall Effect (1995)
Schmeller, A., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
We have employed tilted-field magneto-transport measurements of the energy gap for the odd-integer quantized Hall states at Landau level filling factors $\nu = 1$,3 and 5 to determine the spin of...
Lifetime of Two-Dimensional Electrons Measured by Tunneling Spectroscopy (1995)
Murphy, S. Q., Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
For electrons tunneling between parallel two-dimensional electron systems, conservation of in-plane momentum produces sharply resonant current-voltage characteristics and provides a uniquely...
Schuppler, S., Adler, D.L., Pfeiffer, L.N., West, K.W., Chaban, E.E., Citrin, P.H.
Physical Review B, 51(1995) S.10527-38
Separately contacted electron-hole double layer in a GaAs/AlxGa1−xAs heterostructure (1994)
Kane, B. E., Eisenstein, J. P., Wegscheider, W., Pfeiffer, L. N., West, K. W.
We describe a method for creating closely spaced parallel two-dimensional electron and hole gases confined in 200 Å GaAs wells separated by a 200 Å wide AlxGa1−xAs barrier. Low-temperature ohmic...
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
A quantitative study of the compressibility of the two-dimensional electron gas in GaAs heterostrutures is reported. Using a recently developed capacitive technique that avoids the large offset...
Resonance Magnetoresistance in Coupled Quantum Wells (1994)
Berk, Y., Kamenev, A., Palevski, A., Pfeiffer, L. N., West, K. W.
The in-plane magnetic field suppresses the quantum coupling between electrons in a double quantum well structure. The microscopical theory of this effect is developed and confirmed experimentally. We...
Chang, A. M., Baranger, H. U., Pfeiffer, L. N., West, K. W.
We report experimental evidence that chaotic and non-chaotic scattering through ballistic cavities display distinct signatures in quantum transport. In the case of non-chaotic cavities, we observe a...
Resonant Transport in Coupled Quantum Wells: a Probe for Scattering Mechanisms (1994)
Berk, Y., Kamenev, A., Palevski, A., Pfeiffer, L. N., West, K. W.
We present a microscopical theory and experimental results concerning resistance resonance in two tunneling coupled quantum wells with different mobilities. The shape of the resonance appears to be...
High-mobility transport along single quasi-1D quantum wires formed by cleaved edge overgrowth (1994)
Wegscheider, Werner, Kang, W., Pfeiffer, L. N., West, K. W., Stormer, H. L., Baldwin, K. W.
We report on a novel contact scheme which for the first time makes possible magnetotransport measurements on individual quasi-1D quantum wires prepared by cleaved edge overgrowth. Contacting is...
Many-body integer quantum Hall effect: Evidence for new phase transitions (1994)
Murphy, S. Q., Eisenstein, J. P., Boebinger, G. S., Pfeiffer, L. N., West, K. W.
The ν=1 quantum Hall effect in bilayer 2D electron systems is shown to continuously evolve from a regime dominated by single-particle tunneling into one where interlayer Coulomb interactions...
Evidence for virtual-phonon exchange in semiconductor heterostructures (1993)
Gramila, T. J., Eisenstein, J. P., MacDonald, A. H., Pfeiffer, L. N., West, K. W.
Measurements of frictional drag between adjacent electron gases in double quantum wells provide strong evidence for phonon-mediated electron-electron interactions. These interactions, which dominate...
Cleaved edge overgrowth for quantum wire fabrication (1993)
Pfeiffer, Loren, Stormer, H. L., Baldwin, K. W., West, K. W., Goñi, A. R., Pinczuk, A., ...
We review a new molecular beam epitaxy (MBE) technique we call cleaved edge overgrowth (CEO), which makes possible fabrication of quantum wires or other lower dimensional quantum structures with...
Lasing from excitons in quantum wires (1993)
Pfeiffer, L. N., Dignam, M. M., Pinczuk, A., West, K. W., Wegscheider, Werner, McCall, S. L., ...
Stimulated optical emission from the lowest exciton state in atomically smooth semiconductor quantum wires is observed for the first time. The wires are formed by the ssT intersection of two 7 nm...
Coulomb barrier to tunneling between parallel two-dimensional electron systems (1992)
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Tunneling between parallel two-dimensional electron gases in double quantum wells is examined at both zero and high perpendicular magnetic field. The measured I-V characteristics show the magnetic...
Multiquantum well structure with an average electron mobility of 4.0×10^6 cm^2/V s (1992)
Pfeiffer, L. N., West, K. W., Eisenstein, J. P., Baldwin, K. W., Gammel, P.
We report a modulation-doped multiquantum well structure which suppresses the usual ambient light effect associated with modulation doping. Ten GaAs quantum wells 300-Å wide are symmetrically...
New fractional quantum Hall state in double-layer two-dimensional electron systems (1992)
Eisenstein, J. P., Boebinger, G. S., Pfeiffer, L. N., West, K. W., He, Song
Transport studies on bilayer two-dimensional electron systems in GaAs double quantum wells have revealed a new fractional quantum Hall state that has no known counterpart in a single-layer 2D system....
Negative compressibility of interacting two-dimensional electron and quasiparticle gases (1992)
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Direct measurements of the compressibility K of the 2D electron gas at both zero magnetic field B and in the high-field extreme quantum limit, ν
Probing a two-dimensional Fermi surface by tunneling (1991)
Eisenstein, J. P., Gramila, T. J., Pfeiffer, L. N., West, K. W.
Equilibrium tunneling between parallel two-dimensional electron systems is measured as a function of in-plane magnetic field and sheet density. For equal two-dimensional densities the tunnel...
Field-induced resonant tunneling between parallel two-dimensional electron systems (1991)
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
Resonant tunneling between two high-mobility two-dimensional (2D) electron systems in a double quantum well structure has been induced by the action of an external Schottky gate field. Using one 2D...
Mutual friction between parallel two-dimensional electron systems (1991)
Gramila, T. J., Eisenstein, J. P., MacDonald, A. H., Pfeiffer, L. N., West, K. W.
Frictional drag between isolated two-dimensional electron gases separated by a thin barrier has been observed at low temperatures in GaAs/AlGaAs double-quantum-well structures. Separate electrical...
Independently contacted two-dimensional electron systems in double quantum wells (1990)
Eisenstein, J. P., Pfeiffer, L. N., West, K. W.
A new technique for creating independent ohmic contacts to closely spaced two-dimensional electron systems in double quantum well (DQW) structures is described. Without use of shallow diffusion or...
Formation of a high quality two-dimensional electron gas on cleaved GaAs (1990)
Pfeiffer, Loren, West, K. W., Stormer, H. L., Eisenstein, J. P., Baldwin, K. W., Gershoni, D., ...
We have succeeded in fabricating a two-dimensional electron gas (2DEG) on the cleaved (110) edge of a GaAs wafer by molecular beam epitaxy (MBE). A (100) wafer previously prepared by MBE growth is...
Evidence for a spin transition in the ν=2/3 fractional quantum Hall effect (1990)
Eisenstein, J. P., Stormer, H. L., Pfeiffer, L. N., West, K. W.
Magnetotransport measurements on a low-density two-dimensional electron system have revealed a re-entrant dependence of the activation energy on magnetic field for the fractional quantum Hall state...
Evidence for a phase transition in the fractional quantum Hall effect (1989)
Eisenstein, J. P., Stormer, H. L., Pfeiffer, L., West, K. W.
We observe a novel transition between distinct fractional quantum Hall states sharing the same filling fraction ν=8/5. The transition is driven by tilting the two-dimensional electron-gas sample...
Pattern Formation Resulting from Faceted Growth in Zone Melted Thin Films (1985)
Saarloos, W. Van, Pfeiffer, L., Paine, S., Gilmer, G.H., West, K.W.
Pattern Formation Resulting from Faceted Growth in Zone Melted Thin Films (1985)
Saarloos, W. Van, Pfeiffer, L., Paine, S., Gilmer, G.H., West, K.W.
Differential adhesion of amino acids to inorganic surfaces
Willett, R. L., Baldwin, K. W., West, K. W., Pfeiffer, L. N.
A fundamental, yet underexplored, materials system is the interface between biological molecules and inorganic surfaces. In an elemental approach to this problem, we have systematically examined the...
Dalla Vecchia, L K, Grosfeld, J L, West, K W, Rescorla, F J, Scherer, L R, Engum, S A
OBJECTIVE: The authors evaluate reoperation for recurrent gastroesophageal reflux (GER) after a failed Nissen fundoplication. SUMMARY BACKGROUND DATA: Nissen fundoplication is an accepted treatment...
Grosfeld, J L, Chaet, M, Molinari, F, Engle, W, Engum, S A, West, K W, ...
OBJECTIVE: The authors evaluated the risk of necrotizing enterocolitis (NEC) in very low birth weight infants receiving indomethacin (INDO) to close patent ductus arteriosus (PDA). BACKGROUND DATA:...
Delayed surgical repair and ECMO improves survival in congenital diaphragmatic hernia.
West, K W, Bengston, K, Rescorla, F J, Engle, W A, Grosfeld, J L
One hundred ten infants with congenital diaphragmatic hernia (CDH) developed life-threatening respiratory distress in the first 6 hours of life. Associated anomalies were present in 33%. Twenty-eight...
Changing trends in necrotizing enterocolitis. Experience with 302 cases in two decades.
Grosfeld, J L, Cheu, H, Schlatter, M, West, K W, Rescorla, F J
Three hundred two infants with necrotizing enterocolitis (NEC) were treated from 1972 to 1990. One hundred eighteen were treated medically while 184 infants required operation. Comparisons were made...
Differential adhesion of amino acids to inorganic surfaces
Willett, R. L., Baldwin, K. W., West, K. W., Pfeiffer, L. N.
A fundamental, yet underexplored, materials system is the interface between biological molecules and inorganic surfaces. In an elemental approach to this problem, we have systematically examined the...
Dalla Vecchia, L K, Grosfeld, J L, West, K W, Rescorla, F J, Scherer, L R, Engum, S A
OBJECTIVE: The authors evaluate reoperation for recurrent gastroesophageal reflux (GER) after a failed Nissen fundoplication. SUMMARY BACKGROUND DATA: Nissen fundoplication is an accepted treatment...
Grosfeld, J L, Chaet, M, Molinari, F, Engle, W, Engum, S A, West, K W, ...
OBJECTIVE: The authors evaluated the risk of necrotizing enterocolitis (NEC) in very low birth weight infants receiving indomethacin (INDO) to close patent ductus arteriosus (PDA). BACKGROUND DATA:...
Delayed surgical repair and ECMO improves survival in congenital diaphragmatic hernia.
West, K W, Bengston, K, Rescorla, F J, Engle, W A, Grosfeld, J L
One hundred ten infants with congenital diaphragmatic hernia (CDH) developed life-threatening respiratory distress in the first 6 hours of life. Associated anomalies were present in 33%. Twenty-eight...
Changing trends in necrotizing enterocolitis. Experience with 302 cases in two decades.
Grosfeld, J L, Cheu, H, Schlatter, M, West, K W, Rescorla, F J
Three hundred two infants with necrotizing enterocolitis (NEC) were treated from 1972 to 1990. One hundred eighteen were treated medically while 184 infants required operation. Comparisons were made...
Willett, R. L., Pfeiffer, L. N., West, K. W.
A standing problem in low-dimensional electron systems is the nature of the 5/2 fractional quantum Hall (FQH) state: Its elementary excitations are a focus for both elucidating the state's properties...