Vibrationally resolved optical excitations of the nitrogen-vacancy center in diamond

TL;DR

This paper develops a theoretical framework using spin-flip time-dependent density functional theory to accurately predict vibrationally resolved optical spectra of the nitrogen-vacancy center in diamond, aligning well with experimental data.

Contribution

It introduces a general approach for calculating excited singlet states of spin defects, enhancing understanding of their optical properties and interactions with phonons.

Findings

Excellent agreement with experimental spectra

Identification of key phonons influencing absorption

Highlighting non-adiabatic effects in optical processes

Abstract

A comprehensive description of the optical cycle of spin defects in solids requires the understanding of the electronic and atomistic structure of states with different spin multiplicity, including singlet states which are particularly challenging from a theoretical standpoint. We present a general framework, based on spin-flip time-dependent density function theory, to determine the excited state potential energy surfaces of the many-body singlet states of spin defects; we then predict the vibrationally resolved absorption spectrum between singlet shelving states of a prototypical defect, the nitrogen-vacancy center in diamond. Our results, which are in excellent agreement with experiments, provide an interpretation of the measured spectra and reveal the key role of specific phonons in determining absorption processes, and the notable influence of non-adiabatic interactions. The insights gained from our calculations may be useful in defining strategies to improve infrared-absorption-based magnetometry and optical pumping schemes. The theoretical framework developed here is general and applicable to a variety of other spin defects and materials.