Quantum Sensors in Two-Dimensional Materials: Advantages and Applications

The recent discovery of optical spin defects in two-dimensional (2D) materials, such as boron-vacancy center (V_B) in hexagonal boron nitride (hBN), presents a brand new angle to construct solid-state quantum sensors. In principle, the atomic-thin structure of the host materials can enable the spin qubits to be placed sub-nanometer away from the target samples to be measured, facilitating the imaging of inter-facial phenomena with unprecedented sensitivity and spatial resolution. Despite such promise, the relatively broad spin transitions and short quantum coherence time observed in 2D quantum sensors substantially limit their sensing capabilities. Therefore, a natural question arises: Can 2D quantum sensors really outperform their 3D counterparts, such as nitrogen-vacancy (NV) centers in diamond. In this talk, we will address this open question. In particular, by choosing the optimal isotope selections of the host hBN, namely ¹⁵N and ¹⁰B, we observe substantially narrower and less crowded V_B transitions as well as extended coherence time T₂ and relaxation time T₁. Armed with these improved 2D quantum sensors, we explore two directions where 2D systems may surpass 3D NV-based sensors: (1) the imaging of local temperatures and the investigation of interfacial spin-phonon coupling, and (2) the integration of 2D sensors into diamond anvil cells for stress and magnetism measurements in high-pressure environment.