Valley-magnetophonon resonance for interlayer excitons

TL;DR

This paper reports the discovery of a valley-magnetophonon resonance in heterobilayer MoSe2/WSe2, revealing how magnetic fields and phonons influence interlayer exciton properties, with implications for valleytronics.

Contribution

It uncovers an intrinsic valley-magnetophonon resonance in interlayer excitons caused by intervalley hole scattering mediated by chiral phonons.

Findings

Resonance occurs at 24.2 Tesla in different stacking configurations.

Intervalley hole scattering involves chiral TA phonons of MoSe2.

Resonance enhances photoluminescence polarization degree.

Abstract

Heterobilayers consisting of MoSe$_2$ and WSe$_2$ monolayers can host optically bright interlayer excitons with intriguing properties such as ultralong lifetimes and pronounced circular polarization of their photoluminescence due to valley polarization, which can be induced by circularly polarized excitation or applied magnetic fields. Here, we report on the observation of an intrinsic valley-magnetophonon resonance for localized interlayer excitons promoted by invervalley hole scattering. It leads to a resonant increase of the photoluminescence polarization degree at the same field of 24.2 Tesla for H-type and R-type stacking configurations despite their vastly different excitonic energy splittings. As a microscopic mechanism of the hole intervalley scattering we identify the scattering with chiral TA phonons of MoSe$_2$ between excitonic states mixed by the long-range electron hole exchange interaction.