Electrically Tunable Localized versus Delocalized Intralayer Moir\'e Excitons and Trions in a Twisted MoS$_2$ Bilayer

TL;DR

This study investigates how twist angles in MoS2 bilayers influence localized and delocalized moiré excitons and trions, demonstrating electrical tunability and revealing complex valley coherence behaviors relevant for many-body physics.

Contribution

It provides the first detailed analysis of electrically tunable localized versus delocalized intralayer moiré excitons and trions in twisted MoS2 bilayers at marginal twist angles.

Findings

Identification of localized and delocalized moiré excitons.

Electrical modulation of excitonic properties and resonant Raman scattering.

Valley coherence exhibits non-monotonic gating dependence.

Abstract

Moir\'e superlattice-induced sub-bands in twisted van der Waals homo- and hetero-structures govern their optical and electrical properties, rendering additional degrees of freedom such as twist angle. Here, we demonstrate the moir\'e superlattice effects on the intralayer excitons and trions in a twisted bilayer of MoS$_2$ of H-type stacking at marginal twist angles. We identify the emission from localized and multiple delocalized sub-bands of intralayer moir\'e excitons and show their electrical modulation by the corresponding trion formation. The electrical control of the oscillator strength of the moir\'e excitons also results in a strong tunability of resonant Raman scattering. We find that the gate-induced doping significantly modulates the electronic moir\'e potential, however leaves the excitonic moir\'e confinement unaltered. This effect, coupled with variable moir\'e trap filling by tuning the optical excitation density, allows us to delineate the different phases of localized and delocalized moir\'e trions. We demonstrate that the moir\'e excitons exhibit strong valley coherence that changes in a striking non-monotonic W-shape with gating due to motional narrowing. These observations from the simultaneous electrostatic control of quasiparticle-dependent moir\'e potential will lead to exciting effects of tunable many-body phenomena in moir\'e superlattices.