论文标题
压力诱导的间隙调制和扭曲双层和双双层石墨烯中的拓扑转换
Pressure induced gap modulation and topological transitions in twisted bilayer and double bilayer graphene
论文作者
论文摘要
我们在垂直压力下研究了完全松弛的扭曲双层（TBG）和双双层（TDBG）石墨烯的电子和拓扑特性。已经提出了一种方法，以获得平衡的面内结构变形和在压力下Moiré超级晶格中的平面瓦楞纸。我们发现，在较高的压力下，平面内放松变得更强大，而每一层的波纹高度都保持不变。放松和刚性结构的带结构之间的比较表明，不仅电子和孔边的间隙（$δ_e$和$Δ_H$）在没有放松的情况下被大大低估了，而且刚性结构的中间束缚的详细分散剂与宽松系统的详细分散相当不同。 $δ_e$和$Δ_H$ TBG的$δ_H$达到最狭窄的中间带的关键压力周围的最大值。拓扑转变在压力下发生在TDBG中，中价和一个山谷触摸中的导带，其Chern数量彼此传递。压力还可以调节TDBG中立点处的间隙，该间隙在压力范围内关闭并在较高压力下重新开放。在压力下，超级工业的电子结构的行为对扭曲角度$θ$敏感，临界压力通常会随$θ$而增加。
We study the electronic and topological properties of fully relaxed twisted bilayer (TBG) and double bilayer (TDBG) graphene under perpendicular pressure. An approach has been proposed to obtain the equilibrium in-plane structural deformation and out-of-plane corrugation in moiré superlattices under pressure. We find that the in-plane relaxation becomes much stronger under higher pressure, while the corrugation height in each layer is maintained. The comparison between band structures of relaxed and rigid structures demonstrates that not only the gaps on the electron and hole sides ($Δ_e$ and $Δ_h$) are significantly underestimated without relaxation but also the detailed dispersions of the middle bands of rigid structures are rather different from those of relaxed systems. $Δ_e$ and $Δ_h$ in TBG reach maximum values around critical pressures with narrowest middle bands. Topological transitions occur in TDBG under pressure with the middle valence and conduction bands in one valley touching and their Chern numbers transferred to each other. The pressure can also tune the gap at the neutrality point of TDBG, which becomes closed for a pressure range and reopened under higher pressure. The behavior of electronic structure of supertlattices under pressure is sensitive to the twist angle $θ$ with the critical pressures generally increase with $θ$.
