石墨烯中Kekulé序、平带与电子-声子耦合的相互作用

中文摘要 AI 辅助

已知石墨烯中的Kekulé序会在范霍夫奇点（VHS）附近产生扩展平带，并增强电子-声子耦合。然而，这些效应共存的微观机制仍不清楚。本文表明，它们共同出现是晶格畸变的结果，这种畸变通过碳键的差异化和相关的电子跳跃得以体现。在此图景下，M点附近的导带宽度随Kekulé序增强而近似线性减小，而范霍夫奇点和无量纲电子-声子耦合则呈现近似二次方的上升响应。由此产生的电子-声子耦合增强主要受范霍夫奇点处态密度增加所支配，而有效形变势受畸变影响较弱。因此，所得结果与先前相关的理论和实验研究一致，同时也表明在特征性的1/4填充下导带可能变浅，以及超越常规Migdal近似的非绝热电子-声子效应日益重要。总之，这些发现凸显了受控Kekulé序在工程化石墨烯中涌现关联量子相方面的潜力。

英文摘要

The Kekulé order in graphene is known to give rise to extended flat bands near the van Hove singularity (VHS) and enhanced electron-phonon coupling. However, the microscopic mechanism underlying the coexistence of these effects remains unclear. Here, it is shown that they jointly emerge as a consequence of the lattice distortion manifested through the differentiation of carbon bonds and associated electronic hoppings. In this picture, the conduction band around the $M$ point decreases almost linearly in width with increasing Kekulé order, while the VHS and dimensionless electron-phonon coupling exhibit approximately quadratic upward responses. The resulting enhancement of the electron-phonon coupling is governed predominantly by the increasing density of states at the VHS, with the effective deformation potential remaining weakly affected by the distortion. As such, the obtained results are consistent with previous related theoretical and experimental studies, while also pointing toward a potential shallowing of the conduction band under the characteristic $1/4$ filling and an increasing relevance of nonadiabatic electron-phonon effects beyond the conventional Migdal approximation. Altogether, these findings highlight the potential of controlled Kekulé ordering for engineering emergent correlated quantum phases in graphene.

发表机构

• Institute of Physics, Faculty of Science and Technology, Jan Długosz University in Czȩstochowa（琴斯托霍瓦扬·德乌戈什大学科学与技术学院物理研究所）

机构由 AI 辅助整理，请以论文原文为准。

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6 pages, 4 figures