Excitonic Collapse in Semiconducting Transition Metal Dichalcogenides

TL;DR

This paper investigates excitonic phenomena in 2D semiconducting transition metal dichalcogenides, revealing a generic exciton collapse effect in strong coupling regimes that merges bound states into the continuum.

Contribution

It introduces the concept of exciton collapse in STMDCs and demonstrates its generic occurrence in these 2D materials.

Findings

Excitons in STMDCs can collapse into the band continuum under strong coupling.

The exciton collapse is a universal feature in these 2D crystals.

The phenomenon impacts the optical and electronic properties of STMDCs.

Abstract

Semiconducting transition metal dichalcogenides (STMDC) are two-dimensional (2D) crystals characterized by electron volt size band gaps, spin-orbit coupling (SOC), and d-orbital character of its valence and conduction bands. We show that these materials carry unique exciton quasiparticles (electron-hole bound states) with energy within the gap but which can ``collapse'' in the strong coupling regime by merging into the band structure continuum. The exciton collapse seems to be a generic effect in these 2D crystals.