Probing Complex Many-Body Interactions in 2D Heterostructures

Two-dimensional (2D) materials provide unprecedented opportunity to engineer their physical properties by modification to the electronic structure utilizing external perturbations- strain, gating, adsorbates, defects, twist-angle, and interface engineering. This is expected to cause changes to the Hamiltonian describing the system and has resulted in exotic phenomena such as superconductivity, bound quasiparticles, topological states as well as magnetic phases, with implications for novel electronics and spin-device applications. In this talk, I will present our work on directly visualizing (without any assumption) the electronic structure of atomically thin systems utilizing <i>in-operando</i> angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES) on 2D heterostructures and their fully functional devices. I will present the experiments which demonstrate on-demand tuning of the electronic band structure in atomically thin systems, such as transition metal dichalcogenides (TMDs) and graphene, by varying the twist-angle between the atomic layers and external dopants. Specifically, I will discuss the electric field tuning of the electronic interactions that result in van Hove singularity and flat bands in twisted bilayer graphene and twisted double bilayer graphene heterostructures. In addition, I will discuss our results where we observe the formation of quasiparticle polarons due to many-body interactions in graphene/TMDs heterostructures.