Photoluminescence at the ground state level anticrossing of the nitrogen-vacancy center in diamond

TL;DR

This paper explores the photoluminescence signatures of NV centers in diamond at the ground state level anticrossing, revealing how various environmental factors influence optical signals and enabling advancements in microwave-free quantum sensing applications.

Contribution

It provides a comprehensive analysis of the PL signatures of NV centers under different environmental couplings at GSLAC, including new insights into nuclear spin polarization and defect concentration measurement.

Findings

Distinct PL signatures for different spin environments at GSLAC

Nuclear spins can be polarized via NV centers at GSLAC

Potential for improved defect sensing and quantum applications

Abstract

The nitrogen-vacancy center (NV center) in diamond at magnetic fields corresponding to the ground state level anticrossing (GSLAC) region gives rise to rich photoluminescence (PL) signals due to the vanishing energy gap between the electron spin states, which enables to have an effect on the NV center's luminescence for a broad variety of environmental couplings. In this article we report on the GSLAC photoluminescence signature of NV ensembles in different spin environments at various external fields. We investigate the effects of transverse electric and magnetic fields, P1 centers, NV centers, and the $^{13}$C nuclear spins, each of which gives rise to a unique PL signature at the GSLAC. The comprehensive analysis of the couplings and related optical signal at the GSLAC provides a solid ground for advancing various microwave-free applications at the GSLAC, including but not limited to magnetometry, spectroscopy, dynamic nuclear polarization (DNP), and nuclear magnetic resonance (NMR) detection. We demonstrate that not only the most abundant $^{14}$NV center but the $^{15}$NV can also be utilized in such applications and that nuclear spins coupled to P1 centers can be polarized directly by the NV center at the GSLAC, through a giant effective nuclear $g$-factor arising from the NV center-P1 center-nuclear spin coupling. We report on new alternative for measuring defect concentration in the vicinity of NV centers and on the optical signatures of interacting, mutually aligned NV centers.