Fractional corner charges induced by fragile topology in threefold symmetric two-dimensional materials

Abstract: We perform a systematic study of the signatures of fragile topology in a number of nonmagnetic two-dimensional materials belonging to space group 164, most of them transition metal dichalcogenides. Using group theory analysis in the framework of topological quantum chemistry, we find fragile bands near the Fermi level for all the materials studied. Since stable topological bands are also present in these systems, the interplay of both phases is discussed, showing that corner charges appear in nearly three quarters of the materials and that they are caused by fragile topology. Using first-principles calculations, we predict corner states with fractional corner charges protected by C3 symmetry. Our work aims to broaden the scope of materials with experimentally accessible fragile bands.