An optical investigation of interacting excitons electrons in van der Waals heterostructures

Abstract

Two dimensional (2D) materials with the unique confinement and reduced screening effect have become compelling platforms for investigating electron interactions. Among these, 2D semiconducting transition metal dichalcogenides (TMDs) stand out due to their strong light matter interaction, direct bandgap exhibited at monolayer and valley selection behavior. These characteristics make TMDs suitable for observing excitonic effects and probing intricate interplay between excitons and electrons through optical measurement. After aligning layers of TMDs and building heterostructures, the formation of moiré superlattices offers an enhanced platform to study electron-electron, exciton-electron, and exciton-exciton interactions. This thesis presents our optical investigation into intra- and interlayer excitons in TMD heterostructures, focusing primarily on WSe2/MoSe2 and WSe2/WS2 heterostructure. In the WSe2/MoSe2 heterostructures, we have observed the formation of interlayer moiré trions (exciton-hole and exciton-electron quasiparticle). Subsequently, in our investigation of WSe2/WS2, we have identified a distinctive configuration of interlayer excitons. Moreover, by increasing the optical excitation power, we have observed correlated bosonic states through strong onsite dipole-dipole interactions between interlayer excitons. Furthermore, we investigated the formation of magnetic orders and magnetic interactions in WSe2/WS2 from the exchange interactions between the excitons and the moiré trapped holes. Collectively, these works unveil the rich interplay and diverse states arising from the interactions between excitons and other particles within TMD heterostructures.