Sub-Terahertz Spin Relaxation Dynamics of Boron-Vacancy Centers in Hexagonal Boron Nitride

TL;DR

This paper demonstrates that boron-vacancy centers in hexagonal boron nitride can serve as quantum sensors operating at sub-terahertz frequencies and high magnetic fields, revealing new spin relaxation dynamics and enabling advanced quantum sensing applications.

Contribution

It introduces the use of $ ext{V}_ ext{B}^-$ centers in hBN as quantum sensors in the sub-terahertz, high-field regime, extending the operational frequency range of spin-based sensors.

Findings

V_B^- centers operate up to 0.2 THz as quantum sensors.

Observed a crossover in relaxation behavior at high fields.

Identified single-phonon-induced resonant noise at sub-terahertz frequencies.

Abstract

Quantum sensors based on spin-defect relaxation have become powerful tools for detecting faint magnetic signals, yet their operation has remained largely confined to low magnetic fields and gigahertz frequencies. Extending such sensors into high-field ($> 0.3$ T) and sub-terahertz regimes would enable quantum metrology across a wide range of electromagnetic phenomena and scientific applications, but has proven challenging. Here, we demonstrate that negatively charged boron vacancies ($\mathrm{V_B^-}$) in two-dimensional hexagonal boron nitride can function as relaxation-based quantum sensors operating up to 0.2 terahertz. Their uniform spin-orientation and persistent spin-contrast at high fields enable direct measurement of intrinsic spin relaxation across previously unexplored temperature and frequency regimes. We also reveal a crossover in relaxation behavior \textemdash initially decreasing at low fields before rising at higher fields \textemdash consistent with the emergence of single-phonon-induced resonant noise that becomes significant at sub-terahertz frequencies. These results establish $\mathrm{V_B^-}$ centers as a versatile platform for quantum sensing in the sub-terahertz, high-field regime.