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arXiv 2602.22705cond-mat.str-el
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方格子Hubbard模型中金属-绝缘体交叉的量子蒙特卡洛研究

Quantum Monte Carlo study of the metal-insulator crossover in the square-lattice Hubbard model

University of Science and Technology of China(中国科学技术大学);Institute of Modern Physics, Northwest University(西北大学现代物理研究所)

Mingzhong Lu, Yu-Feng Song, Youjin Deng, Yuan-Yao He

AI总结:

使用辅助场量子蒙特卡洛方法,无偏研究半填充方格子Hubbard模型在有限温度下从费米液体到Mott绝缘体的交叉,建立温度-相互作用相图,揭示Bad Metal区间和节点-反节点二分性,并给出热熵图和Pomeranchuk冷却参数区域。

摘要:

从费米液体到Mott绝缘体的相互作用驱动演化是强关联费米子系统的标志。在这项工作中,我们使用辅助场量子蒙特卡洛方法,对半填充方格子Hubbard模型在有限温度下的金属-绝缘体交叉进行了{\it 数值无偏}研究。通过联合分析热力学和动力学可观测量,我们建立了模型在温度-相互作用($T$-$U$)平面上的交叉图。随着$U$的增加,我们的数值结果揭示了一个扩展的交叉区域,我们称之为{\it Bad Metal},它将费米液体和Mott绝缘体分开。在交叉过程中,我们还检查了反铁磁自旋关联,并观察到动量分辨单粒子谱函数中显著的节点-反节点二分性。此外,我们研究了模型中几个常用可观测量的温度依赖性。作为代表性结果,我们获得了交叉图上热熵的精确映射,并确定了模型表现出Pomeranchuk冷却(其特征是随着$U$增加而绝热冷却)的参数区域。我们的工作不仅提供了对交叉现象的更精细理解,还为未来关于方格子Hubbard模型的光学晶格实验提供了有价值的基准和指导。

英文摘要:

The interaction-driven evolution from a Fermi liquid to a Mott insulator is a hallmark of strongly correlated fermion systems. In this work, we present a {\it numerically unbiased} study of such metal-to-insulator crossover in the half-filled square-lattice Hubbard model at finite temperatures, employing auxiliary-field quantum Monte Carlo method. By jointly analyzing thermodynamic and dynamical observables, we establish the crossover diagram of the model in the temperature-interaction ($T$-$U$) plane. With increasing $U$, our numerical results reveal an extended crossover regime, which we refer to as the {\it Bad Metal}, that separates the Fermi liquid and Mott insulator. During the crossover, we also examine the antiferromagnetic spin correlations and observe pronounced nodal-antinodal dichotomy in the momentum-resolved single-particle spectral functions. Furthermore, we investigate the temperature dependence of several commonly used observables in the model. As representative results, we achieve an accurate map of the thermal entropy across the crossover diagram, and identify the parameter regions in which the model exhibits the Pomeranchuk cooling, characterized by an adiabatic cooling with increasing $U$. Beyond offering a more refined understanding of the crossover phenomenon, our work also provides valuable benchmark and guideline for future optical lattice experiments on the square-lattice Hubbard model.

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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