Energy transfer from tunneling electrons to excitons

TL;DR

This paper demonstrates a novel electrically driven method to generate excitons in transition metal dichalcogenides via energy transfer from tunneling electrons, expanding possibilities for optoelectronic device design.

Contribution

It introduces a new paradigm for exciton creation in van der Waals heterostructures through energy transfer from tunneling electrons, supported by experimental and theoretical evidence.

Findings

Observation of exciton peaks in photoemission spectra

Evidence of energy transfer from tunneling electrons to excitons

Theoretical model confirming inelastic electron tunneling as the mechanism

Abstract

Excitons in optoelectronic devices have been generated through optical excitation, external carrier injection, or employing pre-existing charges. Here, we reveal a new way to electrically generate excitons in transition metal dichalcogenides (TMDs). The TMD is placed on top of a gold-hBN-graphene tunnel junction, outside of the tunneling pathway. This electrically driven device features a photoemission spectrum with a distinct peak at the exciton energy of the TMD. We interpret this observation as exciton generation by energy transfer from tunneling electrons, which is further supported by a theoretical model based on inelastic electron tunneling. Our findings introduce a new paradigm for exciton creation in van der Waals heterostructures and provide inspiration for a new class of optoelectronic devices in which the optically active material is separated from the electrical pathway.