Isolating Exciton Dissociation Pathways in ReSe$_{\text{2}}$

TL;DR

This study uses TR-ARPES to distinguish exciton dissociation mechanisms in ReSe₂, identifying photoionization as the key process and establishing a population-resolved approach for analyzing exciton-to-carrier conversion.

Contribution

It introduces a population-resolved strategy using TR-ARPES to isolate and identify exciton dissociation pathways in strongly excitonic materials.

Findings

Exciton dissociation in ReSe₂ is dominated by photoionization.

Fluence and polarization dependence reveal dissociation mechanisms.

Population-resolved analysis distinguishes competing processes.

Abstract

Strongly bound excitons dominate the optical response in many van der Waals semiconductors, yet distinguishing between the different microscopic processes governing exciton dissociation remains challenging. Using time- and angle-resolved photoemission spectroscopy (TR-ARPES), we independently track exciton and band-edge carrier populations in bulk ReSe$_{\text{2}}$ under resonant excitation. By studying the fluence dependence and polarization-controlled exciton density dependence of the exciton dissociation process, we distinguish between competing processes and identify exciton photoionization as the microscopic dissociation mechanism. These results establish a population-resolved strategy for resolving exciton-to-carrier conversion pathways in strongly excitonic materials.