发表机构
University of Chicago; University of Minnesota Twin Cities; University of California, Berkeley（芝加哥大学; 明尼苏达大学双城分校; 加州大学伯克利分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究推导了纳入结构弛豫的魔角扭转双层石墨烯单粒子连续模型，计算ν=±2时的Hartree-Fock基态，发现-2填充时因弛豫效应出现半金属相，与从头算结果吻合并探讨实验未观测到的原因。
AI 中文摘要
研究魔角扭转双层石墨烯（MATBG）关联电子相图的标准方法是将库仑相互作用投影到仅包含单粒子平带及部分附近远程带电子的有效模型中。我们提供了MATBG单粒子性质的单粒子连续模型的新颖系统推导，该模型纳入了结构弛豫效应且保持在拉格朗日框架内。我们将库仑相互作用投影到该模型平带占据的电子上，并计算填充数ν=±2时的Hartree-Fock多体基态。我们发现，纳入弛豫效应会使模型在-2填充时进入半金属相，原因是弛豫模型的单粒子色散存在粒子-空穴不对称性，且平带波函数变得更集中，导致Hartree势增强。我们的结果证实了近期从头算密度泛函理论研究的结论，即-2填充时存在半金属相。我们还讨论了这类相在实验中未被观测到的潜在原因。
英文摘要
A standard approach for studying magic angle twisted bilayer graphene (MATBG)'s correlated electronic phase diagram is to project the Coulomb interaction down to effective models only involving electrons in single-particle flat bands and some nearby remote bands. We provide a novel systematic derivation of a single-particle continuum model of MATBG's single-particle properties which incorporates structural relaxation while remaining in the Lagrangian frame. We project the Coulomb interactions down to electrons occupying the flat bands of this model and compute the Hartree-Fock many-body ground states at fillings $ν= \pm 2$. We find that incorporating relaxation effects drives the model into a semi-metallic phase at $- 2$ because of particle-hole asymmetry in the relaxed model's single-particle dispersion and because the flat band wavefunctions become more concentrated leading to an enhanced Hartree potential. Our results corroborate recent ab initio density functional theory studies which also found semi-metallic phases at $-2$. We discuss potential explanations for why such phases have not been seen in experiments.
