Single and double quantum transitions in spin-mixed states under photo-excitation

TL;DR

This study investigates single- and double-quantum transitions in NV center spins under photo-excitation, revealing amplified ESR signals and detailed polarization behavior, advancing NV-based sensing and quantum applications.

Contribution

It provides a comprehensive analysis of spin-mixed states in NV centers under off-axis magnetic fields using a seven-level model, including experimental ESR signal amplification.

Findings

Amplification of ESR signals under laser illumination.

Hyperfine-resolved ESR signals depend on laser power and magnetic field alignment.

Detailed understanding of NV spin polarization under off-axis fields.

Abstract

Electronic spins associated with the Nitrogen-Vacancy (NV) center in diamond offer an opportunity to study spin-related phenomena with extremely high sensitivity owing to their high degree of optical polarization. Here, we study both single- and double-quantum transitions (SQT and DQT) in NV centers between spin-mixed states, which arise from magnetic fields that are non-collinear to the NV axis. We demonstrate the amplification of the ESR signal from both these types of transition under laser illumination. We obtain hyperfine-resolved X-band ESR signal as a function of both excitation laser power and misalignment of static magnetic field with the NV axis. This combined with our analysis using a seven-level model that incorporates thermal polarization and double quantum relaxation allows us to comprehensively analyze the polarization of NV spins under off-axis fields. Such detailed understanding of spin-mixed states in NV centers under photo-excitation can help greatly in realizing NV-diamond platform's potential in sensing correlated magnets and biological samples, as well as other emerging applications, such as masing and nuclear hyperpolarization.