Excited State Spectroscopy of Boron Vacancy Defects in Hexagonal Boron Nitride Using Time-Resolved Optically Detected Magnetic Resonance.

Baber, Simon; Malein, Ralph Nicholas Edward; Khatri, Prince; Keatley, Paul Steven; Guo, Shi; Withers, Freddie; Ramsay, Andrew J; Luxmoore, Isaac J · Nano Lett · 2022

basic_science · Level V

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Abstract

We report optically detected magnetic resonance (ODMR) measurements of an ensemble of spin-1 negatively charged boron vacancies in hexagonal boron nitride. The photoluminescence decay rates are spin-dependent, with intersystem crossing rates of 1.02 ns<sup>-1</sup> and 2.03 ns<sup>-1</sup> for the <i>m</i><sub><i>S</i></sub> = 0 and <i>m</i><sub><i>S</i></sub> = ±1 states, respectively. Time gating the photoluminescence enhances the ODMR contrast by discriminating between different decay rates. This is particularly effective for detecting the spin of the optically excited state, where a zero-field splitting of |<i>D</i><sub><i>ES</i></sub>| = 2.09 GHz is measured. The magnetic field dependence of the photoluminescence exhibits dips corresponding to the ground (GSLAC) and excited-state (ESLAC) anticrossings and additional anticrossings due to coupling with nearby spin-1/2 parasitic impurities. Comparison to a model suggests that the anticrossings are mediated by the interaction with nuclear spins and allows an estimate of the ratio of the singlet to triplet spin-dependent relaxation rates of κ<sub>0</sub>/κ<sub>1</sub> = 0.34.