Tuning properties of deep defects in hexagonal boron nitride: an ab-initio study*

In recent years, atom-like deep defects in semiconductors have emerged as promising solid-state qubits (quantum bits) for applications in different quantum technologies. Defects in bulk 3D semiconductors, such as the charged NV-center in diamond and divacancies in SiC, are better-known defects and have been more widely studied. However, increasingly, there is an interest in exploring quantum emitters in layered 2D semiconductors. As compared to a 3D semiconductor, the 2D structure of a layered material offers better control of the location of the deep defect in the 2D-matrix, providing a scalable platform for quantum applications. In addition, the surface-only structure of the layered materials makes it possible to tune their properties and hence, the properties of the defects within the 2D structures. This can be achieved by controlling various factors, such as: (a) the number of the layers and their composition and, (b) the applied strain. The density functional theory-based results presented here show that the deep defects in hexagonal boron nitride (hBN) have high-spin ground states even at room-temperature, making them viable solid-state qubit candidates in a layered material.  We further demonstrate that strain can be used to tune the electronic, spin and optical properties of these quantum emitters within the layers.