自旋费米子和费米赫伯德模型中的相互作用增强嵌套

R. Rossi, F. Šimkovic IV, M. Ferrero, A. Georges, A. M. Tsvelik, N. V. Prokof'ev, I. S. Tupitsyn
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引用次数: 0

摘要

自旋费米子(SF)模型假定,在近临界金属中,低能费米子之间的主要耦合是由内耳波矢量 QN 处的集体自旋波动(准自旋波动)介导的。有观点认为,热点处的强相关性会导致费米表面变形(FSD),其特点是平坦区域和嵌套增加。这一猜想在微扰自洽计算中得到了证实,即当动量偏离 QN 的参量传播者依赖性由 χ-1∝|Δq| 给出时。我们使用图解蒙特卡洛(diagMC)技术表明,这种依赖性只在温度比问题中任何其他能量尺度都小的数量级上成立,这表明可能有不同的机制在起作用。相反,我们发现,χ-1∝|Δq|2 依赖性产生了实现 FSD 的稳健有限 T 方案。为了将现象学描述与微观描述联系起来,我们将连通行列式 diagMC 方法应用于(t-t′)哈伯德模型,发现在大 U/t>5。5时,在电子和空穴形成之前,(i) 定义为谱函数最大值的FSD并不十分明显;相反,是重正化色散关系的零点线向嵌套方向变形;(ii) 静态自旋易感性由χ-1∝|Δq|2很好地描述。平坦的 FS 区域产生了实现非费米液态的非难方案。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Interaction-enhanced nesting in spin-fermion and Fermi-Hubbard models

Interaction-enhanced nesting in spin-fermion and Fermi-Hubbard models
The spin-fermion (SF) model postulates that the dominant coupling between low-energy fermions in near critical metals is mediated by collective spin fluctuations (paramagnons) peaked at the Néel wave vector, QN, connecting hot spots on opposite sides of the Fermi surface. It has been argued that strong correlations at hot spots lead to a Fermi surface deformation (FSD) featuring flat regions and increased nesting. This conjecture was confirmed in the perturbative self-consistent calculations when the paramagnon propagator dependence on momentum deviation from QN is given by χ1|Δq|. Using diagrammatic Monte Carlo (diagMC) technique we show that such a dependence holds only at temperatures orders of magnitude smaller than any other energy scale in the problem, indicating that a different mechanism may be at play. Instead, we find that a χ1|Δq|2 dependence yields a robust finite-T scenario for achieving FSD. To link phenomenological and microscopic descriptions, we applied the connected determinant diagMC method to the (tt) Hubbard model and found that at large U/t>5.5 before the formation of electron and hole pockets (i) the FSD defined as a maximum of the spectral function is not very pronounced; instead, it is the lines of zeros of the renormalized dispersion relation that deforms toward nesting, and (ii) the static spin susceptibility is well described by χ1|Δq|2. Flat FS regions yield a nontrivial scenario for realizing a non-Fermi liquid state.
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