A first-principles exploration of the effect of Se vacancies on the topological surface states of Bi₂Se₃

In this work, we elucidate the effects of the most common intrinsic defect, Se vacancies, on the topological surface states of Bi₂Se₃. We explore in detail how the position of the defect affects the surface states. In addition to finding perfectly preserved topologically protected surface states in the presence of neutral Se vacancies, we see that the Dirac cone shifts deep into the valence band. Furthermore, we report for the first-time the emergence of a band pinned near the Fermi level that exhibits signs of non-linear dispersion. We discuss the possible origins of this departure from linearity. Our results bring us a step closer to understanding the exotic physics emerging from defects in Bi₂Se₃ that had remained unexplored in prior studies.