Topological interfacial states in ferroelectric domain walls of two-dimensional bismuth

Abstract

Using machine learning method, we investigate various domain walls for the recently discovered single-element ferroelectrics bismuth monolayer [Nature 617, 67 (2023)]. Surprisingly, we find that the charged domain wall configuration has a lower energy than the uncharged domain wall structure due to its low electrostatic repulsion potential. Two stable charged domain wall configurations exhibit topological interfacial states near their domain walls, which is caused by the change of the Z_2 number between ferroelectric and paraelectric states. Interestingly, different from the edge states of topological insulators, the topological interfacial states related Dirac bands are contributed from different edges which is caused by the build-in electric field of FE. Our works thus indicate that domain walls in two-dimensional bismuth can be a good platform for ferroelectric domain wall devices.Comment: 15 pages, 4 fig