Theory & Simulation of Twisted Bilayer Materials

近年来，扭转双分子膜作为一种研究强关联电子性质的新平台出现了。在这些系统中，两片2D材料以扭曲的角度堆叠在一起，产生具有周期性的莫尔图案，其长度尺度可以比底层原子晶格的长度尺度大几个数量级。莫尔图案产生的超晶格势降低了电子的动能，并导致了个别层中不存在的相关感应现象的出现，如磁性、绝缘行为，甚至非传统超导。虽然扭转双层石墨烯是研究最深入的扭转双层体系，因为在实验中发现了超导电性，当掺杂相关绝缘态时，具有一定的魔力扭曲角，但还有很大的空间可以通过堆积其他二维材料来形成扭转双层体系，如过渡金属二卤化物(TMDCs)和六方氮化硼(h-BN)。这类系统的特性在很大程度上仍未得到探索。在这个项目中，我们将使用理论和模拟(包括紧束缚和多体方法)来研究包括TMDCs、h-BN和石墨烯的候选扭曲双层体系的电学和光学性质，并试图揭示这些体系中超导电性的本质。

Recently, twisted bilayers of two-dimensional (2D) materials have emerged as a new platform for studying the properties of strongly-correlated electrons. In these systems, two sheets of 2D materials are stacked on top of each other with a twist angle, resulting in a Moiré pattern with a periodicity that has a length-scale that can be orders of magnitude larger than that of the underlying atomic lattices. The Moire' pattern induces a superlattice potential which reduces the kinetic energy of electrons and results in the emergence of correlation-induced phenomena absent in the individual layers, such as magnetism, insulating behaviour or even unconventional superconductivity. Whilst twisted bilayer graphene is the most intensely studied twisted bilayer system due to the experimental discovery of superconductivity upon doping the correlated insulator state at certain "magic" twist angles, there is a large space of promising twisted bilayer systems that can be formed by stacking other 2D materials such as transition metal dichalcogenides (TMDCs) and hexagonal boron nitride (h-BN). The properties of such systems remain largely unexplored. In this project, we will use theory and simulation (including tight-binding and many-body methods) to investigate the electronic and optical properties of candidate twisted bilayer systems involving TMDCs, h-BN and graphene and attempt to unravel the nature of superconductivity in these systems.