Excited-state spectroscopy of spin defects in hexagonal boron nitride

TL;DR

This study used ODMR to explore the excited-state spin properties of boron vacancy defects in hexagonal boron nitride at room temperature, revealing key parameters relevant for quantum technologies.

Contribution

It provides the first direct measurement of excited-state spin transitions in VB- defects in hBN using ODMR at room temperature.

Findings

Excited state has a zero-field splitting of ~2.1 GHz.

Hyperfine interactions are observed at ~90 MHz and ~18.8 MHz.

Magnetic field dependence reveals insights into spin dynamics.

Abstract

We used optically detected magnetic resonance (ODMR) technique to directly probe electron-spin resonance transitions in the excited state of negatively-charged boron vacancy (VB-) defects in hexagonal boron nitride (hBN) at room temperature. The data showed that the excited state has a zero-field splitting of ~ 2.1 GHz, a g factor similar to the ground state and two types of hyperfine splitting ~ 90 MHz and ~ 18.8 MHz respectively. Pulsed ODMR experiments were conducted to further verify observed resonant peaks corresponding to spin transitions in the excited state. In addition, negative peaks in photoluminescence and ODMR contrast as a function of magnetic field magnitude and angle at level anti-crossing were observed and explained by coherent spin precession and anisotropic relaxation. This work provided significant insights for studying the structure of VB- excited states, which might be used for quantum information processing and nanoscale quantum sensing.