Optical responses of boron-vacancy defects in strained hexagonal boron nitride*

The recently discovered negatively charged boron vacancy defects in hexagonal boron nitride (h-BN), a layered van der Waals material, have great potential for applications of quantum qubit and sensing. However, neutral boron vacancy (VB) and negatively charged boron vacancy (VB^-) have similar photoluminescence spectrum, which makes it hard to distinguish VB and VB^- by usual optical characteristic tools. In this work, we report first-principles calculation of electronic band structures and optical absorption spectrum of VB and VB^- single point defects in monolayer h-BN under external strain. We find that VB and VB^- defects exhibit different optical responses to external strain, which may assist to probe the defect types. Meanwhile, the enhanced change of optical spectra of defects in strained h-BN may work for the application of strain sensors.