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Multi-Chain Mean-Field Theory of Quasi One-Dimensional Quantum Spin Systems

Anders W. Sandvik

cond-mat.str-elarXiv:cond-mat/9904218

Abstract

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 C0 is modeled by a number of neighbor chains Cd, d = +/-1,...,+/-n, with the edge chains (d=+/-n) coupled to a staggered field. Using a quantum Monte Carlo method, the effective (2n+1)-chain Hamiltonian is solved self-consistently for n up to 4. The results are compared with simulation results for the original Hamiltonian on large rectangular lattices. Both methods show that the staggered magnetization M for small interchain couplings alpha behaves as M=A*alpha1/2 enhanced by a multiplicative logarithmic correction.

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