Elucidating the Inter-system Crossing of the Nitrogen-Vacancy Center up to Megabar Pressures

TL;DR

This paper combines first principles calculations and high-pressure experiments to understand how stress influences the optical and inter-system crossing properties of nitrogen-vacancy centers in diamond, especially under megabar pressures.

Contribution

It provides a comprehensive microscopic framework for NV center behavior under stress, resolving key open questions and enabling stress-based tuning of quantum sensors.

Findings

Revealed the complex behavior of inter-system crossing rates under stress.

Explained the contrast enhancement in (111)-oriented anvils.

Accounted for contrast inversion in high-pressure regimes.

Abstract

The integration of Nitrogen-Vacancy color centers into diamond anvil cells has opened the door to quantum sensing at megabar pressures. Despite a multitude of experimental demonstrations and applications ranging from quantum materials to geophysics, a detailed microscopic understanding of how stress affects the NV center remains lacking. In this work, using a combination of first principles calculations as well as high-pressure NV experiments, we develop a complete description of the NV's optical properties under general stress conditions. In particular, our ab initio calculations reveal the complex behavior of the NV's inter-system crossing rates under stresses that both preserve and break the defect's symmetry. Crucially, our proposed framework immediately resolves a number of open questions in the field, including: (i) the microscopic origin of the observed contrast-enhancement in (111)-oriented anvils, and (ii) the surprising observation of NV contrast-inversion in certain high-pressure regimes. Our work lays the foundation for optimizing the performance of NV high-pressure sensors by controlling the local stress environment, and more generally, suggests that symmetry-breaking stresses can be utilized as a novel tuning knob for generic solid-state spin defects.