Probing Many-Body Interactions in Monolayer Transition-Metal Dichalcogenides

TL;DR

This study investigates many-body interactions in monolayer transition-metal dichalcogenides, revealing how intervalley plasmons influence exciton energy shifts differently in electron- and hole-doped samples, supported by experimental and analytical modeling.

Contribution

The paper introduces an analytical model that explains exciton energy shifts in monolayer TMDs by incorporating intervalley plasmons, highlighting their role in doping-dependent many-body effects.

Findings

Blueshift of neutral excitons is significant in electron-doped samples but negligible in hole-doped samples.

Intervalley plasmons significantly influence exciton energy renormalization.

The model's predictions agree with experimental measurements, showing material-specific differences.

Abstract

Many-body interactions in monolayer transition-metal dichalcogenides are strongly affected by their unique band structure. We study these interactions by measuring the energy shift of neutral excitons (bound electron-hole pairs) in gated WSe$_2$ and MoSe$_2$. Surprisingly, while the blueshift of the neutral exciton, $X^0$, in electron-doped samples can be more than 10~meV, the blueshift in hole-doped samples is nearly absent. Taking into account dynamical screening and local-field effects, we present a transparent and analytical model that elucidates the crucial role played by intervalley plasmons in electron-doped conditions. The energy shift of $X^0$ as a function of charge density is computed showing agreement with experiment, where the renormalization of $X^0$ by intervalley plasmons yields a stronger blueshift in MoSe$_2$ than in WSe$_2$ due to differences in their band ordering.