Electronic topological transition of 2D boron by the ion exchange reaction

Abstract

We systematically investigated electronic evolutions of non-symmorphic borophene with chemical environments that were realized by the ion exchange method. Electronic structures can be characterized by the topological Z 2 invariant. Spectroscopic experiments and DFT calculations unveiled that a sheet of hydrogenated borophene (borophane) is the Dirac nodal loop semimetal (Z 2 =-1), while a layered crystal of YCrB 4 is an insulator (Z 2 = 1). The results demonstrate the electronic topological transition by replacement of the counter atoms on the non-symmorphic borophene layer.