Time-averaging within the excited state of the nitrogen-vacancy centre in diamond

TL;DR

This study investigates how the emission intensity of nitrogen-vacancy centers in diamond varies with magnetic field and temperature, revealing a temperature-dependent averaging process that affects the excited state structure.

Contribution

It introduces a model that explains the transition from strain-dependent to strain-independent behavior of NV centers with temperature, reconciling low and high temperature observations.

Findings

Low temperature responses depend on sample and stress.

High temperature responses are strain independent.

A temperature-dependent averaging process decouples orbit and spin.

Abstract

The emission intensity of diamond samples containing nitrogen-vacancy centres are measured as a function of magnetic field along a <111> direction for various temperatures. At low temperatures the responses are sample and stress dependent and can be modeled in terms of the previous understanding of the 3E excited state fine structure which is strain dependent. At room temperature the responses are largely sample and stress independent, and modeling involves invoking a strain independent excited state with a single zero field splitting of 1.42 GHz. The change in behaviour is attributed to a temperature dependent averaging process over the components of the excited state orbital doublet. It decouples orbit and spin and at high temperature the spin levels become independent of any orbit splitting. Thus the models can be reconciled and the parameters for low and high temperatures are shown to be consistent.