Excited-state spin-resonance spectroscopy of V$_\text{B}^-$ defect centers in hexagonal boron nitride

Abstract

The recently discovered spin-active boron vacancy (V − B ) defect center in hexagonal boron nitride (hBN) has high contrast optically-detected magnetic resonance (ODMR) at room-temperature, with a spin-triplet ground-state that shows promise as a quantum sensor. Here we report temperaturedependent ODMR spectroscopy to probe spin within the orbital excited-state. Our experiments determine the excited-state spin Hamiltonian, including a room-temperature zero-field splitting of 2.1 GHz and a g-factor similar to that of the ground-state. We confirm that the resonance is associated with spin rotation in the excited-state using pulsed ODMR measurements, and we observe Zeemanmediated level anti-crossings in both the orbital ground-and excited-state. Our observation of a single set of excited-state spin-triplet resonance from 10 to 300 K is consistent with an orbital-singlet, which has consequences for understanding the symmetry of this defect. Additionally, the excited-state ODMR has strong temperature dependence of both contrast and transverse anisotropy splitting, enabling promising avenues for quantum sensing.

Excited-State Spectroscopy of Spin Defects in Hexagonal Boron Nitride

“…While finalizing this paper, we became aware of three complementary works on temperature dependence 25,26 and relaxation rates 27…”

Spin defects in hexagonal boron nitride for strain sensing on nanopillar arrays

“…[16][17][18] A particular spin defect that garners significant attention is the negatively charged boron vacancy (V B − ). [19][20][21][22][23][24][25][26][27][28][29][30][31] The V B − spin can be initialized, manipulated, and read out optically, with coherence times on the order of several microseconds at room temperature. 17 The V B − defect has a triplet ground state with a zero-field splitting (ZFS) D gs /h of ∼3.46 GHz and a broad emission around 800 nm.…”

Nuclear spin polarization and control in a van der Waals material

“…1(a), a V − B spin defect is formed by missing a boron atom in the hBN lattice. The V − B defect has a spin triplet ground state (GS) with a zero-field splitting (ZFS) of D GS = 3.45 GHz [18], and a spin triplet excited state (ES) with ZFS of D ES = 2.1 GHz [39][40][41][42]. The spin-dependent state recombination and photon emission allow optical initialization and readout of the electron spin state (Supplementary Fig.…”