低维量子海森堡反铁磁体的自旋Hartree-Fock方法
Spin Hartree-Fock approach to quantum Heisenberg antiferromagnets in low dimensions
摘要：
利用四点关联函数的Hartree-Fock解耦方法，我们构造了一维和二维量子（自旋为1/2）海森堡反铁磁体的平均场论。结果表明，基于两点关联函数的自洽方程的解不产生符合Mermin-Wagner定理的非物理有限温度相变，这与基于序参量的平均场方程的一般方法不同.在此方法中计算的次近邻自旋-自旋关联函数，在一维中再现了通过Bethe变换得到的强量子涨落重整化，在二维中再现了经典反铁磁态的小重整化.热容量以合理的精度近似于一维中所有温度下的完整贝特安纳伯格结果。在2D中，我们得到了在有限的温度下，可以访问高阶$1/T$扩展的热容的峰值高度的减少。
英文摘要：
We construct a new mean-field theory for 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 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 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.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
