Native Defects in Antiferromagnetic Topological Insulator MnBi${}_2$Te${}_4$

Abstract

Using scanning tunneling microscopy and spectroscopy, we visualized the native defects in antiferromagnetic topological insulator $\mathrm{MnB}{\mathrm{i}}_2\mathrm{T}{\mathrm{e}}_4$. Two native defects $\mathrm{M}{\mathrm{n}}_{\mathrm{Bi}}$ and $\mathrm{B}{\mathrm{i}}_{\mathrm{Te}}$ antisites can be well resolved in the topographic images. $\mathrm{M}{\mathrm{n}}_{\mathrm{Bi}}$ tend to suppress the density of states at conduction band edge. Spectroscopy imaging reveals a localized peak-like local density of state at $\sim 80$~meV below the Fermi energy. A careful inspection of topographic and spectroscopic images, combined with density functional theory calculation, suggests this results from $\mathrm{B}{\mathrm{i}}_{\mathrm{Mn}}$ antisites at Mn sites. The random distribution of $\mathrm{M}{\mathrm{n}}_{\mathrm{Bi}}$ and $\mathrm{B}{\mathrm{i}}_{\mathrm{Mn}}$ antisites results in spatial fluctuation of local density of states near the Fermi level in $\mathrm{MnB}{\mathrm{i}}_2\mathrm{T}{\mathrm{e}}_4$.

6 pages, 4 figures