Self-trapped interlayer excitons in van der Waals heterostructures

TL;DR

This paper investigates the microscopic mechanisms behind self-trapped interlayer excitons in van der Waals heterostructures, revealing how their binding energies and spectral shifts depend on structural parameters and exciton-phonon interactions.

Contribution

It provides a detailed analysis of the self-trapped states of interlayer excitons, classifies them into two types, and explains their spectral behaviors and transformations in vdW heterostructures.

Findings

Self-trapped interlayer excitons are classified into two types based on binding energy behavior.

The spectral shifts of IXs are explained by the type of self-trapped state.

Structural parameters can induce transformation between the two types of self-trapped IXs.

Abstract

The self-trapped state (STS) of interlayer exciton (IX) has been aroused enormous interesting owing to their significant impact on the fundamental properties of the van derWaals heterostructures (vdWHs). Nevertheless, the microscopic mechanisms of STS are still controversial. Herein, we study the corrections of the binding energies of the IXs due to the exciton-interface optical phonon coupling in four kinds of vdWHs and find that these IXs are in the STS for the appropriate ratio of the electron and hole effective masses. We show that these STSs could be classified into the type I with the increasing binding energy in the tens of meV range, which are very agreement with the red-shift of the IXs spectra in experiments, and the type II with the decreasing binding energy, which provides a possible explanation for the blue-shift and broad linewidth of the IXs spectra in the low temperature. Moreover, these two types of self-trapped IXs could be transformed into each other by adjusting the structural parameters of vdWHs. These results not only provide an in-depth understanding for the self-trapped mechanism of IX, but also shed light on the modulations of IXs in vdWHs.