Manipulating the Charge State of Spin Defects in Hexagonal Boron Nitride

Negatively charged boron vacancies ($V_B^{-}$) in hexagonal boron nitride (hBN) have recently gained interest as spin defects for quantum information processing and quantum sensing by a layered material. However, the boron vacancy can exist in a number of charge states in the hBN lattice, but only the -1 state has spin-dependent photoluminescence and acts as a spin-photon interface. Here, we investigate charge state switching of $V_B$ defects under laser and electron beam excitation. We demonstrate deterministic, reversible switching between the -1 and 0 states ($V_B^{-}\rightleftharpoons V_B^0+e^{-}$), occurring at rates controlled by excess electrons or holes injected into hBN by a layered heterostructure device. Our work provides a means to monitor and manipulate the $V_B$ charge state, and to stabilize the -1 state which is a prerequisite for optical spin manipulation and readout of the defect.