准一维自旋Hartree-Fock近似下各向异性海森堡反铁磁体的Heat capacity
Heat capacity of anisotropic Heisenberg antiferromagnet within the spin Hartree-Fock approach in quasi-1D Regime
摘要：
研究了自旋为1/2的各向异性量子海森堡反铁磁体，它在一维和二维极限之间平滑地插值。利用自旋Hartree-Fock方法，我们在准一维体系中建立了一个自旋链间有限耦合的热容定量理论。该理论精确地再现了Bethe Anglands在一维极限下的结果，并且在有限温度下，对于准一维范围内的任何各向异性，不产生任何虚假的相变，这与Mermin-Wagner定理一致。我们研究了静态自旋-自旋关联函数，以分析晶格几何和各向异性在这些系统中的相互作用。我们比较了正方形和三角形格子。对于后者，我们发现在$\sim0.6$的中间各向异性处存在量子跃迁点。这种量子相变建立了准一维制度延伸到这个几何形状中的一个特定点。对于正方形晶格，从1D到2D的变化作为各向异性的函数平滑地发生，即它是交叉类型的。比较新开发的理论，现有的实验数据的热容量的$\rm{Cs}_2\rm{CuBr}_4$和$\rm{Cs}_2\rm{CuCl}_4$，我们提取的微观常数的交换相互作用，以前只能使用非弹性中子散射在高磁场。
英文摘要：
We study the anisotropic quantum Heisenberg antiferromagnet for spin-1/2 that interpolates smoothly between the one-dimensional (1D) and the two-dimensional (2D) limits. Using the spin Hartree-Fock approach we construct a quantitative theory of heat capacity in the quasi-1D regime with a finite coupling between spin chains. This theory reproduces closely the exact result of Bethe Ansatz in the 1D limit and does not produces any spurious phase transitions for any anisotropy in the quasi-1D regime at finite temperatures in agreement with the Mermin-Wagner theorem. We study the static spin-spin correlation function in order to analyse the interplay of lattice geometry and anisotropy in these systems. We compare the square and triangular lattice. For the latter we find that there is a quantum transition point at an intermediate anisotropy of $\sim0.6$. This quantum phase transition establishes that the quasi-1D regime extends upto a particular point in this geometry. For the square lattice the change from the 1D to 2D occurs smoothly as a function of anisotropy, i.e. it is of the crossover type. Comparing the newly developed theory to the available experimental data on the heat capacity of $\rm{Cs}_2\rm{CuBr}_4$ and $\rm{Cs}_2\rm{CuCl}_4$ we extract the microscopic constants of the exchange interaction that previously could only be measured using inelastic neutron scattering in high magnetic fields.
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。
