Plasmons and screening in a monolayer of MoS$_2$

TL;DR

This paper studies the dielectric properties and plasmon behavior in monolayer MoS$_2$, revealing how doping, band gap, and spin-orbit effects influence collective excitations and screening phenomena.

Contribution

It provides a detailed analysis of plasmons and screening in monolayer MoS$_2$, highlighting differences from graphene and the impact of spin-orbit coupling.

Findings

Plasmons in MoS$_2$ are affected by intraband transitions similar to 2D electron gases.

Doping causes plasmon energies to differ between p- and n-type MoS$_2$.

Spin-orbit interaction leads to beating of Friedel oscillations at high carrier densities.

Abstract

We investigate the dynamical dielectric function of a monolayer of molybdenum disulfide within the random phase approximation. While in graphene damping of plasmons is caused by interband transitions, due to the large direct band gap in monolayer MoS$_2$ collective charge excitations enter the intraband electron hole continuum similar to the situation in two-dimensional electron and hole gases. Since there is no electron-hole symmetry in MoS$_2$, the plasmon energies in p- and n-doped samples clearly differ. The breaking of spin degeneracy caused by the large intrinsic spin-orbit interaction leads to a beating of Friedel oscillations for sufficiently large carrier concentrations, for holes as well as for electrons.