Excited-state optically detected magnetic resonance of spin defects in hexagonal boron nitride

TL;DR

This paper investigates the excited-state spin properties of boron vacancy centers in hexagonal boron nitride, revealing key parameters like zero-field splitting and ODMR contrast, crucial for quantum technology applications.

Contribution

It provides the first detailed measurement of excited-state zero-field splitting and ODMR contrast in VB- centers in hBN, advancing understanding of their spin dynamics.

Findings

Zero-field splitting in excited state: 2160 MHz

ODMR contrast of 12% at cryogenic temperature

Prominent emission change at cryo-temperature due to ESLAC

Abstract

Negatively charged boron vacancy (VB-) centers in hexagonal boron nitride (hBN) are promising spin defects in a van der Waals crystal. Understanding the spin properties of the excited state (ES) is critical for realizing dynamic nuclear polarization. Here, we report zero-field splitting in the ES of DES = 2160 MHz and an optically detected magnetic resonance (ODMR) contrast of 12% at cryogenic temperature. The ES has a g-factor similar to the ground state. The ES photodynamics is further elucidated by measuring the level anti-crossing of the VB- defects under varying external magnetic fields. In contrast to nitrogen vacancy (NV-) centers in diamond, the emission change caused by excited-state level anti-crossing (ESLAC) is more prominent at cryo-temperature than at room temperature. Our results provide important information for utilizing the spin defects of hBN in quantum technology.