Honeycomb Sb layers on Cu(111) and parities of the surface states

Abstract

The performed DFT study of the electronic structure of honeycomb Sb monolayer adsorbed on the Cu(111) surface has confirmed previous observations of significant role of tensile strain and related reduced buckling of adsorbed layer. The simulated STM pictures are perfectly consistent with those observed in experiment. We show that a significant band mixing with the substrate, which leads to an absence of occupied surface states at M point, questions applicability of the method of determination of the topological invariant Z2 by means of estimates of the products of the parity eigenvalues. Hence, since the adsorption interaction with a metal surface is rather strong, the transformations of the bands of free honeycomb Sb layers with increasing lattice constants, which was recently suggested to cause the transition to the topological insulator state for certain range of the tensile strain, do not directly correspond to the changes which occur for adsorbed layers.