Room temperature coherent control of spin defects in hexagonal boron nitride

Abstract

Optically active spin defects are promising candidates for solid-state quantum information and sensing applications. To use these defects in quantum applications coherent manipulation of their spin state is required. Here, we realize coherent control of ensembles of boron vacancy centers in hexagonal boron nitride (hBN). Specifically, by applying pulsed spin resonance protocols, we measure a spin-lattice relaxation time of 18 microseconds and a spin coherence time of 2 microseconds at room temperature. The spin-lattice relaxation time increases by three orders of magnitude at cryogenic temperature. By applying a method to decouple the spin state from its inhomogeneous nuclear environment the optically detected magnetic resonance linewidth is substantially reduced to several tens of kilohertz. Our results are important for the employment of van der Waals materials for quantum technologies, specifically in the context of high resolution quantum sensing of two-dimensional heterostructures, nanoscale devices, and emerging atomically thin magnets.

Spin defects in hBN as promising temperature, pressure and magnetic field quantum sensors

“…The results presented in this work were obtained on single-crystal hBN. The centers were generated in the sample via neutron irradiation ( 2.3 × 10 18 n cm −2 ), as described elsewhere 16 , 20 . More specifically, the absolute number of defects was determined as 10 13 spins by electron paramagnetic resonance in the dark, giving the defect density of 5.4 × 10 17 cm −3 .…”

“…Accordingly: where is the electronic Landé factor and is the Bohr magneton, so that , the ODMR contrast for center is R = 0.1%, is the collection efficiency, is the number of active spins, and t = 1 s is taken as measurement time. Since the density is known and we excite a voxel of about 10 μm diameter, we can estimate a number of simultaneously addressed spins, and from the previously measured Rabi oscillations 20 , we derived the dephasing time T 2 * = 100 ns. The value for is limited by both the efficiency of the detection setup and the optical properties of the spin-hosting sample, and is therefore important.…”

“…The resolution of to external magnetic fields is comparable to that of silicon vacancies in SiC, but lower than that of NV centers in diamond. However, we believe that the favorable optical properties of this 2D system, the recent demonstration of coherent control of spins in hBN together with the overcoming of inhomogeneous ODMR line broadening by multifrequency spectroscopy 20 will stimulate the development of advanced pulse protocols 35 and lead to a further increase in the resolution of this sensor. In addition, during the preparation of our manuscript, a relevant work on in hBN was submitted 36 reporting an ODMR contrast of almost 10% and its high-temperature stability up to 600 K. Finally, the unique feature of hBN is its non-disturbing chemical and crystallographic compatibility with many different 2D materials, which gains a new fundamental functionality with the embedded spin centers and allows sensing in heterostructures with high resolution serving as a boundary itself.…”

“…Spin carrying defects have been theoretically predicted and experimentally confirmed in hBN 15 – 19 . Currently, the most understood defect is the negatively-charged boron vacancy center ( ) 20 , which can be readily created by neutron irradiation, ion implantation, or femtosecond laser pulses 21 , 22 . Due to its spin-optical properties, the center is proving to be a promising candidate system for quantum information and nanoscale quantum sensing applications and has thus expanded the already large suite of unique features displayed by 2D materials 13 .…”

Creation of Negatively Charged Boron Vacancies in Hexagonal Boron Nitride Crystal by Electron Irradiation and Mechanism of Inhomogeneous Broadening of Boron Vacancy-Related Spin Resonance Lines

“…All the properties mentioned above are summarized in Figure 1 b. Together with pronounced spin coherence properties [ 28 ], this defect is currently considered to be a very promising candidate for quantum technologies.…”