Spin Hartree-Fock approach to studying quantum Heisenberg antiferromagnets in low dimensions

Article

关键词: LOW-TEMPERATURE BEHAVIOR;    MAGNETIC-FIELD;    2-DIMENSIONAL SYSTEMS;    FINITE-TEMPERATURE;    PHASE-TRANSITIONS;    WAVE THEORY;    CHAIN;    THERMODYNAMICS;    LATTICE;    SUSCEPTIBILITY;   

DOI  :  10.1103/PhysRevB.97.180403

来源: SCIE

【 摘 要 】

We construct a new mean-field theory for a quantum (spin-1/2) Heisenberg antiferromagnet in one (1D) and two (2D) dimensions using a Hartree-Fock decoupling of the four-point correlation functions. We show that the solution to the self-consistency equations based on two-point correlation functions does not produce any unphysical finite-temperature phase transition, in accord with the Mermin-Wagner theorem, unlike the common approach based on the mean-field equation for the order parameter. The next-neighbor spin-spin correlation functions, calculated within this approach, reproduce closely the strong renormalization by quantum fluctuations obtained via a Bethe ansatz in 1D and a small renormalization of the classical antiferromagnetic state in 2D. The heat capacity approximates with reasonable accuracy the full Bethe ansatz result at all temperatures in 1D. In 2D, we obtain a reduction of the peak height in the heat capacity at a finite temperature that is accessible by high-order 1/T expansions.

【 授权许可】

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