Bonding Character as a Descriptor for Huang-Rhys Factors in Optically Active Defects

TL;DR

This paper introduces an orbital-based bonding character descriptor that efficiently estimates Huang-Rhys factors, aiding the design and screening of optically active defects for quantum technologies.

Contribution

The study presents a novel ground state bonding descriptor that predicts Huang-Rhys factors without extensive excited-state or phonon calculations.

Findings

Successfully applied to hBN defects and diamond NV center

Enables high throughput screening of defect candidates

Circumvents complex excited-state and phonon calculations

Abstract

The electron phonon coupling of a defect characterized by its Huang Rhys (HR) factor is a crucial metric determining its excited-state dynamics, relevant to defect applications as qubits and quantum emitters. However, HR factors remain challenging to calculate from first principles, complicated by convergence issues in excited-state relaxation and time consuming phonon calculations. Even when calculated, HR factors lack a rational design principle. Here we show that an orbital-based descriptor can be used to rationalize and efficiently estimate HR factors. Combining this descriptor with a ground state deformation technique allows circumventing both excited state relaxation and full phonon calculations. Specifically, our descriptor for HR factors is constructed using bonding character differences obtained from ground state density functional theory, measured using crystal orbital Hamilton populations. We demonstrate this descriptor for prototypical hBN defects and the diamond NV center. This orbital-based descriptor can be potentially used in high throughput computational screening to identify ideal candidates of spin qubits and SPEs.