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arXiv 2208.04014cond-mat.stat-mechmath-phmath.MPquant-ph
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Haldane-Shastry 型 su($m$) 自旋链的热力学与临界性

Thermodynamics and criticality of su($m$) spin chains of Haldane-Shastry type

Federico Finkel, Artemio González-López

AI总结:

本文研究 Haldane-Shastry 型 su($m$) 自旋链的热力学与临界性,推导出自由能等闭式公式,发现低温行为对应中心荷 $c=m-1$ 的共形场论,并指出仅在反铁磁情形下临界。

摘要:

我们在零化学势下研究了 Haldane-Shastry 型 su($m$) 自旋链的热力学与临界行为,涵盖 $A_{N-1}$ 和 $BC_N$ 两种情况。我们以闭式形式评估了任意 $m$ 值下每自旋的自由能,并由此推导出每自旋的能量、熵和比热的显式公式。特别地,我们发现比热呈现单一肖特基峰,其温度在 $m\lesssim10$ 时可由具有均匀间隔能级的 $m$ 级系统对应的温度很好地近似。我们证明,在低温下,所研究模型的每自旋自由能表现为中心荷 $c=m-1$ 的一维共形场论的行为(唯一的例外是其参数为零的 Frahm-Inozemtsev 链)。然而,通过对基态简并度和低能激发的详细研究,我们得出结论:这些模型仅在反铁磁情况下是临界的,并完全指明了少数例外情况。

英文摘要:

We study the thermodynamics and critical behavior of su($m$) spin chains of Haldane-Shastry type at zero chemical potential, both in the $A_{N-1}$ and $BC_N$ cases. We evaluate in closed form the free energy per spin for arbitrary values of $m$, from which we derive explicit formulas for the energy, entropy and specific heat per spin. In particular, we find that the specific heat features a single Schottky peak, whose temperature is well approximated for $m\lesssim10$ by the corresponding temperature for an $m$-level system with uniformly spaced levels. We show that at low temperatures the free energy per spin of the models under study behaves as that of a one-dimensional conformal field theory with central charge $c=m-1$ (with the only exception of the Frahm-Inozemtsev chain with zero value of its parameter). However, from a detailed study of the ground state degeneracy and the low-energy excitations, we conclude that these models are only critical in the antiferromagnetic case, with a few exceptions that we fully specify.

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