Phonon-assisted luminescence in defect centers from many-body perturbation theory

TL;DR

This paper uses a rigorous many-body perturbation theory approach to analyze phonon-assisted luminescence in defect centers, specifically the boron vacancy in 2D hexagonal boron nitride, revealing phonons' crucial role in luminescence.

Contribution

It introduces a novel, first-principles method to study exciton-phonon interactions in defect centers, surpassing traditional phenomenological models.

Findings

Phonons enable luminescence in otherwise dark defect states.

Symmetry breaking from static Jahn-Teller effect does not explain the 1.5 eV peak.

The approach provides predictive insights into defect luminescence mechanisms.

Abstract

Phonon-assisted luminescence is a key property of defect centers in semiconductors, and can be measured to perform the readout of the information stored in a quantum bit, or to detect temperature variations. The investigation of phonon-assisted luminescence usually employs phenomenological models, such as that of Huang and Rhys, with restrictive assumptions that can fail to be predictive. In this work, we predict luminescence and study exciton-phonon couplings within a rigorous many-body perturbation theory framework, an analysis that has never been performed for defect centers. In particular, we study the optical emission of the negatively-charged boron vacancy in 2D hexagonal boron nitride, which currently stands out among defect centers in 2D materials thanks to its promise for applications in quantum information and quantum sensing. We show that phonons are responsible for the observed luminescence, which otherwise would be dark due to symmetry. We also show that the symmetry breaking induced by the static Jahn-Teller effect is not able to describe the presence of the experimentally observed peak at 1.5 eV.