石墨烯相关体系中的超导电性:量子蒙特卡罗方法的研究

Superconductivity in graphene-related systems:A study of quantum Monte Carlo methods

本文对量子蒙特卡罗方法研究石墨烯相关体系中的超导电性进行了回顾.十多年来,理论上预测超导电性可能出现在掺杂的石墨烯基材料中.对于单层原始石墨烯,当填充在狄拉克点附近时,反铁磁涨落有利于自旋单重态超导电性的形成,但量子蒙特卡罗研究发现由于系统极低的电子态密度,电子关联不足以驱动超导电性.如果将系统掺杂到态密度发散的范霍夫奇点,则可能出现具有p+ip超导配对对称性的非常规超导电性.然而,尽管进行了大量的实验工作,但在单层石墨烯中仍未发现超导电性.最近,在关于转角双层石墨烯的实验中发现了非常规的超导电性.紧随其后,实验上在ABC堆叠的三层石墨烯和其他系统中也发现了超导电性.这些发现引起了众多物理学家的关注.本文回顾了石墨烯中超导态的独特性质,通过实验控制扭曲双层石墨烯和三层石墨烯的超导电性,以及栅极可调关联绝缘体.简单概括了扭曲多层石墨烯中电子关联物态在最近凝聚态物理学中的研究进展.

We review a quantum Monte Carlo approach to study superconductivity in graphene-related systems.The emergence of superconductivity in doped graphene-based materials has been theoretically predicted for over a decade.For single-layer graphene,antiferromagnetic ffuctuations favor the spin-singlet superconductivity when packed near the Dirac point.However,quantum Monte Carlo studies have found electronic correlations to be insufficient to drive superconductivity because of the single-layer graphene’s extremely low electronic density of states.Unconventional superconductivity with p+ip superconducting pairing symmetry is possible if the system is doped to a van Hove singularity,where the density of states diverges.However,despite extensive experimental work,superconductivity has yet to be found in single-layer graphene.Recently,unconventional superconductivity was discovered in experiments on twisted bilayer graphene,followed by the experimental discovery of superconductivity in ABC-stacked trilayer graphene and multilayer graphene systems.These findings have attracted the attention of many physicists.In this study,we review the unique properties of superconducting states in graphene,experimental control of superconductivity in the twisted bilayer and trilayer graphene,and associated gate-tunable insulator.In addition,a brief overview of recent research progress in condensed matter physics in term of electronically correlated states in twisted multilayer graphene is presented.