Title:Oral: Understanding the prevalence of the pseudo Jahn-Teller distortion in defects in hexagonal boron nitride

Since the discovery of quantum emission from defects in hexagonal boron nitride (hBN), theoretical works [1,2] have predicted pseudo Jahn-Teller (pJT) distortion in a few of the candidate defects. We show that the pJT distortion, which occurs in systems with non-degenerate ground state, results from a strong vibronic coupling between the occupied and the unoccupied defect states. In accordance with Bersuker’s analysis, the pJT distortion in defective hBN increases the system’s covalency [3]. Using several prototype defects that undergo pJT, we also create a quantitative measure for this added covalency. This measure helps us to create a greater physical understanding of pJT in hBNs’ defects.