σt-J模型中的鲁棒自旋赝能隙与自旋电荷分离
Robust spin pseudogap and spin-charge separation in the $σt$-$J$ model
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中文总结 AI 辅助
本研究用iPEPS算法探究σt-J模型的有限温度性质，发现其自旋赝能隙特征在掺杂后仍鲁棒，建立的Slave-fermion平均场理论可解释该现象。
中文摘要 AI 辅助
σt-J模型是通过翻转常规t-J模型的自旋向下跃迁项符号得到的，该模型被提出用于消除掺杂空穴与自旋背景之间的强干涉效应，即所谓的相位弦效应。本研究采用无限投影纠缠对态（iPEPS）算法，对比t-J模型及其易平面变体，探究σt-J模型的有限温度性质。研究表明，这些模型具有相似的自旋赝能隙热力学特征：在T*~J处自旋磁化率出现峰值，且比热存在宽峰。张量网络重正化（TNR）进一步提供了有力证据，证明σt-J模型的自旋部分存在 Berezinskii-Kosterlitz-Thouless（BKT）相变，且因U(1)自旋旋转对称性降低，其相变温度T_BKT低于T*。关键的是，与同样表现出BKT相变的t-J模型及其易平面变体不同，这些特征在掺杂后仍保持鲁棒性：掺杂空穴保留甚至增强了xy自旋平面内的反铁磁关联，导致T*和T_BKT对掺杂的依赖较弱。最后，本研究为σt-J模型建立了 Slave-fermion平均场理论，其射影对称群（PSG）基于数值确定的跃迁与配对关联进行选择，该理论可解释掺杂后鲁棒自旋赝能隙的形成机制。
英文摘要
The $σt$-$J$ model, obtained from the usual $t$-$J$ model by flipping the sign of the spin-down hopping term, has been proposed to eliminate the strong interference between doped holes and the spin background, known as the phase string effect. In this work, we investigate the finite-temperature properties of the $σt$-$J$ model using infinite projected entangled-pair state (iPEPS) algorithms, in comparison with the $t$-$J$ model and its easy-plane variants. We show that these models share similar spin-pseudogap thermodynamics, with a maximum in the spin susceptibility at $T^* \sim J$ and a broad specific-heat peak. Tensor network renormalization (TNR) further provides strong evidences for a Berezinskii-Kosterlitz-Thouless (BKT) transition in the spin sector of the $σt$-$J$ model at a lower temperature $T_\text{BKT} < T^*$ due to its reduced $\mathrm{U}(1)$ spin-rotation symmetry. Crucially, in contrast to the $t$-$J$ model and to its easy-plane variants that also exhibit BKT transitions, these signatures remain robust upon doping: the doped holes preserve and even enhance the antiferromagnetic correlations in the $xy$ spin plane, leading to a weak doping dependence of both $T^*$ and $T_\text{BKT}$. Finally, we develop a slave-fermion mean-field theory for the $σt$-$J$ model, whose projective symmetry group (PSG) is selected based on numerically determined hopping and pairing correlations, and show that it explains the robust spin pseudogap upon doping.
