Felipe da Jornada1
Stanford University1
The synthesis of quasi-two-dimensional materials, such as monolayer transition metal dichalcogenides (TMDCs), opened the door to the study of new classes of systems with nanoscale dimensionality confinement and weak electronic screening, leading to strongly enhanced electron interactions. In particular, heterobilayers of such materials host unique physics due to the emergence of a moiré potential that modulates such excitations. However, the interplay between the structural details in such twisted bilayer structures (including atomistic relaxation effects), extrinsic fields, and doping on the excited-state properties of such materials is poorly understood, and often relies on empirically fitted continuum models. In this talk, we present results obtained from recent formalisms and methods we developed to bridge these effects and phenomena. We show how moiré effects can lead to a surprising localization of excitons even for relatively large twist angles (~2°) – associated with a moiré lattice parameter of ~ 6 nm. We also develop a formalism to understand the spectroscopic signatures of moiré-confined excitons, in very good agreement with recent time- and angle-resolved photoemission spectroscopy measurements. We also show a new method to extract accurate moiré potentials from first principles, and show why previous <i>ab initio</i> approaches often yield potential depths that are significantly smaller than those deduced from experiment. Finally, we also show how such realistically deduced potentials lead to moiré-modulated interlayer excitons with qualitatively different characters, offering unique tuning capabilities for excitations in van-der-Waals-stacked materials.