[论文解读] Origin and fate of the pseudogap in the doped Hubbard model

Fedor Šimkovic, Riccardo Rossi+2 more|arXiv (Cornell University)|Sep 19, 2022

Physics of Superconductivity and Magnetism参考文献 41被引用 20

一句话总结

该论文使用受控的图解蒙特卡罗方法来绘制掺杂的二维哈伯模型在有限温度下的相图，确定三个区域（弱相关金属、强相关金属和伪带）并将伪带与自旋涨落以及最终的零温度条带序联系起来。

ABSTRACT

We investigate the doped two-dimensional Hubbard model at finite temperature using controlled diagrammatic Monte Carlo calculations allowing for the computation of spectral properties in the infinite-size limit and, crucially, with arbitrary momentum resolution. We show that three distinct regimes are found as a function of doping and interaction strength, corresponding to a weakly correlated metal with properties close to those of the non-interacting system, a correlated metal with strong interaction effects including a reshaping of the Fermi surface, and a pseudogap regime at low doping in which quasiparticle excitations are selectively destroyed near the antinodal regions of momentum space. We study the physical mechanism leading to the pseudogap and show that it forms both at weak coupling when the magnetic correlation length is large and at strong coupling when it is shorter. In both cases, we show that spin-fluctuation theory can be modified in order to account for the behavior of the non-local component of the self-energy. We discuss the fate of the pseudogap as temperature goes to zero and show that, remarkably, this regime extrapolates precisely to the ordered stripe phase found by ground-state methods. This handshake between finite temperature and ground-state results significantly advances the elaboration of a comprehensive picture of the physics of the doped Hubbard model.

研究动机与目标

• 确定掺杂的二维哈伯模型在有限温度下的跨越/转变作为掺杂和 U 的函数。
• 描述弱相关金属、强相关金属和伪带区域。
• 确定伪带形成的磁相关长度依赖。
• 探索自旋涨落理论是否能描述非局部自能分量。
• 将有限温度下的伪带行为与零温度条带排序联系起来。

提出的方法

• 在热力学极限下使用带任意动量分辨率的受控图解蒙特卡罗方法。
• 通过 A(k)代理和自能计算谱性质，无需解析延拓。
• 将自能分解为局部和非局部部分以分析动量依赖。
• 将非局部自能拟合为受自旋涨落启发的解，chi_sp 采用 Ornstein–Zernike 形式。
• 依据需要与 DMFT 和 DCA 进行比较。

实验结果

研究问题

• RQ1 掺杂的二维哈伯模型在有限温度下的弱相关金属、强相关金属和伪带之间的跨越是什么？
• RQ2 磁相关性和自旋涨落如何驱动伪带，以及这随掺杂和 U 如何演化？
• RQ3 修改后的自旋涨落理论是否能在弱耦合和强耦合下同时捕捉伪带区的非局部自能？
• RQ4 当 T->0 时伪带的命运是什么，是否与基态条带序相联系？

主要发现

• 确定三个区域：弱相关金属、强相关金属和低掺杂伪带（PG）。
• 伪带起源于磁性自旋相关，并随温度和掺杂演变。
• 一个修改后的自旋涨落框架可以描述PG区在弱耦合下的非局部自能，在强耦合下定性描述。
• 伪带边界外推到零温下的条带排序基态，表示与基态结果存在“握手”。
• Fermi面拓扑的 Lifshitz-type 变化伴随伪带，且自旋涨落具有相关长度依赖。
• 在伪带区观察到反节点处的谱权抑制和费米弧形成。