Order-Parameter Correlation Functions in Quantum Critical Phenomena (2007)
We investigate the functional form of the order-parameter (two-point) correlation function in quantum critical phenomena. Contrary to the common lore, when there is no particle-hole symmetry we find...
Finite-temperature phase transitions in a two-dimensional boson Hubbard model (2007)
We study finite-temperature phase transitions in a two-dimensional boson Hubbard model with zero-point quantum fluctuations via Monte Carlo simulations of quantum rotor model, and construct the...
The quasi-particle gap in a disordered boson Hubbard model in two dimensions (2005)
We investigate the behavior of the quasi-particle energy gap near quantum phase transitions in a two-dimensional disordered boson Hubbard model at a commensurate filling. Via Monte Carlo simulations...
Superfluid-insulator transitions of two-species Bosons in an optical lattice (2005)
Isacsson, A., Cha, Min-Chul, Sengupta, K., Girvin, S. M.
We consider a realization of the two-species bosonic Hubbard model with variable interspecies interaction and hopping strength. We analyze the superfluid-insulator (SI) transition for the relevant...
Correlations at a quantum phase transition in interacting Bose systems (2005)
We have investigated the correlation functions of interacting bosons at the generic superfluid-insulator transition, a prototypical quantum phase transition, in two dimensions in the spherical limit....
Separation of two regimes in a disordered boson Hubbard Model (2004)
We study the insulator-to-superfluid transition in a two-dimensional disordered boson Hubbard model at zero temperature for intermediate strength of disorder at commensurate density. Via Monte Carlo...
Strongly correlated quantum dots in weak confinement potentials and magnetic fields (2002)
Cha, Min-Chul, Yang, S. -R. Eric
We explore a strongly correlated quantum dot in the presence of a weak confinement potential and a weak magnetic field. Our exact diagonalization studies show that the groundstate property of such a...
We have studied the rationally frustrated Josephson-junction array model in the square lattice through Monte Carlo simulations of $(2+1)$D XY-model. For frustration $f=1/4$, the model at zero...
Phase diagram of a Disordered Boson Hubbard Model in Two Dimensions (2001)
Lee, Ji-Woo, Cha, Min-Chul, Kim, Doochul
We study the zero-temperature phase transition of a two-dimensional disordered boson Hubbard model. The phase diagram of this model is constructed in terms of the disorder strength and the chemical...
Numerical Test of Disk Trial Wave function for Half-Filled Landau Level (2000)
Yang, S. -R. Eric, Cha, Min-Chul, Han, Jung Hoon
The analyticity of the lowest Landau level wave functions and the relation between filling factor and the total angular momentum severely limits the possible forms of trial wave functions of a disk...
Level Fluctuations and Many-Body Effects in Disorder-Free Quantum Dots (1999)
Cha, Min-Chul, Yang, S. -R. Eric
We have investigated whether many-body effects can induce significant level fluctuations in a disorder-free quantum dot. The closed energy shell structures and relaxation of the Hartree-Fock...
Park, Sung Yong, Lee, Ji-Woo, Cha, Min-Chul, Choi, M. Y., Kim, B. J., Kim, Doochul
We study the zero-temperature phase transitions of a two-dimensional disordered boson Hubbard model at incommensurate boson densities. Via matrix diagonalization and quantum Monte Carlo simulations,...
Peak Effect and the Transition from Elastic to Plastic Depinning (1998)
We demonstrate for the first time an observation of the peak effect in simulations of magnetic vortices in a superconductor. The shear modulus $c_{66}$ of the vortex lattice is tuned by adding a...
Linear Chain of Coupled Quantum Dots (1997)
Kang, Kicheon, Cha, Min-Chul, Yang, S. -R. Eric
A linearly coupled chain of spin-polarized quantum dots is investigated under the condition that the number of electrons is equal to or less than the number of the dots. The chemical potential of the...
We report on the results of molecular dynamics simulation (MD) studies of the classical two-dimensional electron crystal in the presence disorder. Our study is motivated by recent experiments on this...
Orientational Order and Depinning of the Disordered Electron Solid (1994)
We study the ground state of two-dimensional classical electron solids under the influence of modulation-doped impurities by using a simulated annealing molecular dynamics method. By changing the...
Universal conductivity in the boson Hubbard model in a magnetic field (1993)
The universal conductivity at the zero-temperature superconductor-insulator transition of the two-dimensional boson Hubbard model is studied for cases both with and without magnetic field by Monte...