Stacking enabled strong coupling of atomic motion to interlayer excitons in van der Waals heterojunction photodiodes

TL;DR

This paper demonstrates that stacking in van der Waals heterojunctions induces strong exciton-phonon coupling, observable through photocurrent spectroscopy, which impacts interlayer excitations and offers new control strategies in 2D material devices.

Contribution

It reveals stacking-induced strong coupling between atomic motion and interlayer excitons, using photocurrent measurements to uncover vibrational effects in heterostructures.

Findings

Pronounced periodic sidebands in photocurrent spectrum near exciton resonances

Energy increments of sidebands match heterojunction vibrational modes

Strong exciton-phonon coupling affects interlayer excitations

Abstract

We reveal stacking-induced strong coupling between atomic motion and interlayer excitons through photocurrent measurements of WSe$_2$/MoSe$_2$ heterojunction photodiodes. Strong coupling manifests as pronounced periodic sidebands in the photocurrent spectrum in frequency windows close to the interlayer exciton resonances. The sidebands, which repeat over large swathes of the interlayer exciton photocurrent spectrum, occur in energy increments corresponding directly to a prominent vibrational mode of the heterojunction. Such periodic patterns, together with interlayer photoconductance oscillations, vividly demonstrate the emergence of extraordinarily strong exciton-phonon coupling - and its impact on interlayer excitations - in stack-engineered van der Waals heterostructure devices. Our results establish photocurrent spectroscopy as a powerful tool for interrogating vibrational coupling to interlayer excitons and suggest an emerging strategy to control vibronic physics in the solid-state.