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arXiv 2408.16752cond-mat.str-el
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Kondo-Heisenberg 玩具模型:精确结果与自旋波展开的比较

Kondo-Heisenberg toy models: Comparison of exact results and spin wave expansion

M. Frakulla, J. Strockoz, D. S. Antonenko, J. W. F. Venderbos

AI总结:

本文通过一维可解 Kondo-Heisenberg 玩具模型,证明强耦合 1/S 自旋波展开在能量、本征态及自旋极化子描述上与精确解逐阶一致。

摘要:

本文研究一类一维可精确求解的 Kondo-Heisenberg 玩具模型,目标是将铁磁基态的精确低能激发与由自旋波理论得到的近似解进行比较。在此过程中,我们采用最近提出的强耦合 1/S 自旋波展开,该展开有效描述了给定点位上总自旋 S±1/2 的激发(即局域矩与电子自旋之和)。我们还利用了如下事实:具有量子自旋和单个电子的 Kondo 晶格模型的基态是铁磁体,并且该铁磁体的磁激发可以被精确确定。我们证明,在 1/S 和强耦合展开参数 t/J_K 中逐阶来看,自旋波的能量和本征态都与精确解完全一致。在反铁磁 Kondo 耦合的特定情形下,当精确基态波函数描述自旋极化子时,我们表明自旋波形式体系中的电子算符精确对应于自旋极化子态。更广泛地说,对 Kondo-Heisenberg 玩具模型的研究被证明可为巡游 Kondo 磁体与 Heisenberg 磁体之间的根本区别提供洞见。

英文摘要:

In this paper we study a class of exactly solvable Kondo-Heisenberg toy models in one dimension, with the goal of comparing the exact low-energy excitations of the ferromagnetic ground state to the approximate solution obtained from spin wave theory. In doing so we employ a recently introduced strong coupling $1/S$ spin wave expansion, which effectively describes excitations of the total spin $S\pm 1/2$ on a given site (i.e., sum of local moment and electron spin). We further make use of the fact that the ground state of Kondo lattice models with quantum spins and a single electron is a ferromagnet, and that the magnetic excitations of the ferromagnet can be exactly determined. We demonstrate that the energies and eigenstates of the spin waves are in full agreement with the exact solution order-by-order in $1/S$ and $t/J_K$, the strong coupling expansion parameter. In the specific case of antiferromagnetic Kondo coupling, when the exact ground state wave function describes spin polaron, we show that the electron operators of the spin wave formalism precisely correspond to the spin polaron states. More broadly, the study of Kondo-Heisenberg toy models is shown to provide insight into the fundamental distinction between itinerant Kondo magnets and Heisenberg magnets.

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。

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