Wang, Ling, Sandvik, Anders W.
We present several different calculations pertaining to the nature of the low-energy excitations of the site-diluted S=1/2 Heisenberg antiferromagnet, in particular at the percolation point. We...
Plaquette Renormalization Scheme for Tensor Network States (2009)
Wang, Ling, Kao, Ying-Jer, Sandvik, Anders W.
We present a method for contracting a square-lattice tensor network in two dimensions, based on auxiliary tensors accomplishing successive truncations (renormalization) of 8-index tensors for 2 by 2...
Impurity-induced frustration in correlated oxides (2008)
Liu, Cheng-Wei, Liu, Shiu, Kao, Ying-Jer, Chernyshev, A. L., Sandvik, Anders W.
Using the example of Zn-doped La2CuO4, we demonstrate that a spinless impurity doped into a non-frustrated antiferromagnet can induce substantial frustrating interactions among the spins surrounding...
Z4-U(1) crossover of the order parameter symmetry in a two-dimensional valence-bond-solid (2008)
We discuss ground-state projector simulations of a modified two-dimensional S=1/2 Heisenberg model in the valence bonds basis. Tuning matrix elements corresponding to the diagonal and off-diagonal...
Edge effects in the two-dimensional spin-1/2 Heisenberg antiferromagnet (2008)
Hoglund, Kaj H., Sandvik, Anders W.
We use quantum Monte Carlo simulations to study effects of free edges in the two-dimensional spin-1/2 Heisenberg antiferromagnet. We find that the magnetic response of an edge is smaller than the...
Insulator to superfluid transition in coupled photonic cavities in two dimensions (2008)
Zhao, Jize, Sandvik, Anders W., Ueda, Kazuo
A system of coupled photonic cavities on a two-dimensional square lattice is systematically investigated using the stochastic series expansion quantum Monte Carlo method. The ground state phase...
Scale-renormalized matrix-product states for correlated quantum systems (2007)
A generalization of matrix product states (MPS) is introduced which is suitable for describing interacting quantum systems in two and three dimensions. These scale-renormalized matrix-product states...
A two-dimensional lattice hard-core boson system with a small fraction of bosonic or fermionic impurity particles is studied. The impurities have the same hopping and interactions as the dominant...
Emergence of U(1) symmetry in the 3D XY model with Zq anisotropy (2007)
Lou, Jie, Sandvik, Anders W., Balents, Leon
We study the three-dimensional XY model with a Z_q anisotropic term. At temperatures T < Tc this dangerously irrelevant perturbation is relevant only above a length scale Lambda, which diverges as a...
Valence bond solid phases in a cubic antiferromagnet (2006)
Beach, K. S. D., Sandvik, Anders W.
We report on a valence bond projector Monte Carlo simulation of the cubic lattice quantum Heisenberg model with additional higher-order exchange interactions in each unit cell. The model supports two...
Impurity induced spin texture in quantum critical 2D antiferromagnets (2006)
Hoglund, Kaj H., Sandvik, Anders W., Sachdev, Subir
We describe the uniform and staggered magnetization distributions around a vacancy in a quantum critical two-dimensional S=1/2 antiferromagnet. The distributions are delocalized across the entire...
Using ground-state projector quantum Monte Carlo simulations in the valence bond basis, it is demonstrated that non-frustrating four-spin interactions can destroy the Neel order of the...
Wang, Ling, Sandvik, Anders W.
We investigate the quantum dynamics of site diluted S=1/2 Heisenberg antiferromagnetic clusters at the percolation threshold. We use Lanczos diagonalization to calculate the lowest excitation gap...
Quantum-criticality and percolation in dimer-diluted 2D antiferromagnets (2006)
The S=1/2 Heisenberg model is considered on bilayer and single-layer square lattices with couplings J1, J2, and with each spin belonging to one J2-coupled dimer. A transition from a Neel to...
Site dilution of quantum spins in the honeycomb lattice (2006)
Castro, Eduardo V., Peres, N. M. R., Beach, K.S. D., Sandvik, Anders W.
We discuss the effect of site dilution on both the magnetization and the density of states of quantum spins in the honeycomb lattice, described by the antiferromagnetic Heisenberg spin-S model. Since...
Wang, Ling, Beach, K. S. D., Sandvik, Anders W.
We use quantum Monte Carlo (stochastic series expansion) and finite-size scaling to study the quantum critical points of two S=1/2 Heisenberg antiferromagnets in two dimensions: a bilayer and a...
Ground state projection of quantum spin systems in the valence bond basis (2005)
A Monte Carlo method for quantum spin systems is formulated in the basis of valence bond (singlet pair) states. The non-orthogonality of this basis allows for an efficient importance-sampled...
Site dilution of quantum spins in the honeycomb lattice (2005)
Castro, Eduardo V., Peres, N. M. R., Beach, K. S. D., Sandvik, Anders W.
We discuss the effect of site dilution on both the magnetization and the density of states of quantum spins in the honeycomb lattice, described by the antiferromagnetic Heisenberg spin-S model. For...
Data collapse in the critical region using finite-size scaling with subleading corrections (2005)
Beach, K. S. D., Wang, Ling, Sandvik, Anders W.
We propose a treatment of the subleading corrections to finite-size scaling that preserves the notion of data collapse. This approach is used to extend and improve the usual Binder cumulant analysis....
Stochastic series expansion algorithm for the S=1/2 XY model with four-site ring exchange (2004)
Melko, Roger G., Sandvik, Anders W.
We describe a stochastic series expansion (SSE) quantum Monte Carlo method for a two-dimensional S=1/2 XY-model (or, equivalently, hard-core bosons at half-filling) which in addition to the standard...
Hoglund, Kaj H., Sandvik, Anders W.
We discuss effects of various impurities on the magnetic susceptibility and the specific heat of the quantum S=1/2 Heisenberg antiferromagnet on a two-dimensional square lattice. For impurities with...
Crossover effects in the random exchange spin-1/2 antiferromagnetic chain (2003)
Laflorencie, Nicolas, Rieger, Heiko, Sandvik, Anders W., Henelius, Patrik
The random antiferromagnetic spin-1/2 XX and XXZ chain is studied numerically for varying strength of the disorder, using exact diagonalization and stochastic series expansion methods. The spin-spin...
Deconfinement and criticality in extended two-dimensional dimer models (2003)
A square-lattice hard-core dimer model with links extending beyond nearest-neighbors is studied using a directed-loop Monte Carlo method. An arbitrarily small fraction of next-nearest-neighbor dimers...
Magnetic ordering in a doped frustrated spin-Peierls system (2003)
Laflorencie, Nicolas, Poilblanc, Didier, Sandvik, Anders W.
Based on a model of a quasi-one dimensional spin-Peierls system doped with non-magnetic impurities, an effective two-dimensional Hamiltonian of randomly distributed S=1/2 spins interacting via...
The directed-loop algorithm (2003)
Sandvik, Anders W., Syljuasen, Olav F.
The directed-loop scheme is a framework for generalized loop-type updates in quantum Monte Carlo, applicable both to world-line and stochastic series expansion methods. Here, the directed-loop...
Sengupta, Pinaki, Sandvik, Anders W., Singh, Rajiv R. P.
We have used the stochastic series expansion (SSE) quantum Monte Carlo (QMC) method to study the three-dimensional (3D) antiferromagnetic Heisenberg model on cubic lattices with in-plane coupling J...
Stochastic series expansion method for quantum Ising models with arbitrary interactions (2003)
A quantum Monte Carlo algorithm for the transverse Ising model with arbitrary short- or long-range interactions is presented. The algorithm is based on sampling the diagonal matrix elements of the...
Susceptibility of the 2D S=1/2 Heisenberg antiferromagnet with an impurity (2003)
Hoglund, Kaj H., Sandvik, Anders W.
We use a quantum Monte Carlo method (stochastic series expansion) to study the effects of a magnetic or nonmagnetic impurity on the magnetic susceptibility of the two-dimensional Heisenberg...
Multi-critical point in a diluted bilayer Heisenberg quantum antiferromagnet (2002)
The S=1/2 Heisenberg bilayer antiferromagnet with randomly removed inter-layer dimers is studied using quantum Monte Carlo simulations. A zero-temperature multi-critical point (p*,g*) at the...
Quantum Monte Carlo with Directed Loops (2002)
Syljuasen, Olav F., Sandvik, Anders W.
We introduce the concept of directed loops in stochastic series expansion and path integral quantum Monte Carlo methods. Using the detailed balance rules for directed loops, we show that it is...
The two-dimensional antiferromagnetic S=1/2 Heisenberg model with random site dilution is studied using quantum Monte Carlo simulations. Ground state properties of the largest connected cluster on...
Sengupta, Pinaki, Sandvik, Anders W., Campbell, David K.
We use a stochastic series expansion quantum Monte Carlo method to study the phase diagram of the one-dimensional extended Hubbard model at half filling for small to intermediate values of the...
In Phys. Rev. Lett. 84, 4204 (2000) (cond-mat/9905379), Kato et al. presented quantum Monte Carlo results indicating that the critical concentration of random non-magnetic sites in the...
Sandvik, Anders W., Singh, Rajiv R. P.
We use quantum Monte Carlo simulations and numerical analytic continuation to study high-energy spin excitations in the two-dimensional S=1/2 Heisenberg antiferromagnet at low temperature. We present...
The sign problem in Monte Carlo simulations of frustrated quantum spin systems (2000)
Henelius, Patrik, Sandvik, Anders W.
We discuss the sign problem arising in Monte Carlo simulations of frustrated quantum spin systems. We show that for a class of ``semi-frustrated'' systems (Heisenberg models with ferromagnetic...
The two-dimensional antiferromagnetic S=1/2 Heisenberg model with random bond dilution is studied using quantum Monte Carlo simulation at the percolation threshold (50% of the bonds removed)....
Multi-Chain Mean-Field Theory of Quasi One-Dimensional Quantum Spin Systems (1999)
A multi-chain mean-field theory is developed and applied to a two-dimensional system of weakly coupled S=1/2 Heisenberg chains. The environment of a chain C_0 is modeled by a number of neighbor...
Sandvik, Anders W., Hamer, Chris J.
We present high-precision quantum Monte Carlo results for the S=1/2 XY model on a two-dimensional square lattice, in the ground state as well as at finite temperature. The energy, the spin stiffness,...
Monte Carlo study of a two-dimensional quantum ferromagnet (1999)
Henelius, Patrik, Sandvik, Anders W., Timm, Carsten, Girvin, S. M.
We present quantum Monte Carlo results for the field and temperature dependence of the magnetization and the spin-lattice relaxation rate $1/T_1$ of a two-dimensional $S=1/2$ quantum Heisenberg...
Stochastic series expansion method with operator-loop update (1999)
A cluster update (the ``operator-loop'') is developed within the framework of a numerically exact quantum Monte Carlo method based on the power series expansion of exp(-BH) (stochastic series...
Spin-Peierls transition in the Heisenberg chain with finite-frequency phonons (1999)
Sandvik, Anders W., Campbell, David K.
We study the spin-Peierls transition in a Heisenberg spin chain coupled to optical bond-phonons. Quantum Monte Carlo results for systems with up to N=256 spins show unambiguously that the transition...
Possible Exotic Phases in the One-Dimensional Extended Hubbard Model (1998)
Clay, R. Torsten, Sandvik, Anders W, Campbell, David K
We investigate numerically the ground state phase diagram of the one-dimensional extended Hubbard model, including an on--site interaction U and a nearest--neighbor interaction V. We focus on the...
Possible Exotic Phases in the One-Dimensional Extended Hubbard Model (1998)
Clay, R. Torsten, Sandvik, Anders W., Campbell, David K.
We investigate numerically the ground state phase diagram of the one-dimensional extended Hubbard model, including an on--site interaction U and a nearest--neighbor interaction V. We focus on the...
The role of winding numbers in quantum Monte Carlo simulations (1997)
Henelius, Patrik, Girvin, S. M., Sandvik, Anders W.
We discuss the effects of fixing the winding number in quantum Monte Carlo simulations. We present a simple geometrical argument as well as strong numerical evidence that one can obtain exact ground...
Two-Dimensional Quantum Ferromagnets (1997)
Timm, Carsten, Henelius, Patrik, Sandvik, Anders W., Girvin, S. M.
We present 1/N Schwinger boson and quantum Monte Carlo calculations of the magnetization and NMR relaxation rate for the two-dimensional ferromagnetic Heisenberg model representing a quantum Hall...
NMR relaxation rates for the spin-1/2 Heisenberg chain (1995)
The spin-lattice relaxation rate $1/T_1$ and the spin echo decay rate $1/T_{2G}$ for the spin-$1\over 2$ antiferromagnetic Heisenberg chain are calculated using quantum Monte Carlo and maximum...
Quantum-Critical Behavior in a Two-Layer Antiferromagnet (1995)
Sandvik, Anders W., Chubukov, Andrey V., Sachdev, Subir
We analyze quantum Monte Carlo data in the vicinity of the quantum transition between a Neel state and a quantum paramagnet in a two-layer, square lattice spin 1/2 Heisenberg antiferromagnet. The...
Disorder Induced Phase Transition in a Random Quantum Antiferromagnet (1994)
Sandvik, Anders W., Vekic, Marco
A two-dimensional Heisenberg model with random antiferromagnetic nearest-neighbor exchange is studied using quantum Monte Carlo techniques. As the strength of the randomness is increased, the system...