Dynamical screening effects of substrate phonons on two-dimensional excitons

TL;DR

This paper demonstrates how substrate phonons dynamically screen excitons in 2D materials, significantly reducing their binding energies, with an analytic model applied to hBN-encapsulated WSe2.

Contribution

It introduces an analytic model for substrate phonon coupling to 2D excitons, highlighting dynamical screening effects on exciton properties.

Findings

Substrate optical phonons influence 2D excitons through dynamical screening.

The model predicts a significant reduction in exciton binding energies.

Application to hBN-encapsulated WSe2 shows notable exciton energy shifts.

Abstract

Atomically thin materials are exceedingly susceptible to their dielectric environment. For transition metal dichalcogenides, sample placement on a substrate or encapsulation in hexagonal boron nitride (hBN) are frequently used. In this paper we show that the dielectric response due to optical phonons of adjacent materials influences excitons in 2d crystals. We provide an analytic model for the coupling of 2d charge carriers to optical substrate phonons, which causes polaron effects similar to that of intrinsic 2d phonons. We apply the model to hBN-encapsulated WSe2, finding a significant reduction of the exciton binding energies due to dynamical screening effects.