Evolution of the electronic structure in ultrathin Bi(111) films

Abstract

By combining angle-resolved photoemission spectroscopy and first-principles calculations, we systematically studied the electronic structures of ultrathin Bi(111) films ($\ensuremath{\le}5$ bilayers) epitaxially grown on ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$. High-resolution low-energy band dispersions and Fermi surfaces of ultrathin $\mathrm{Bi}(111)/{\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ films as a function of thickness were experimentally determined. Our results also indicate that the electronic structures of epitaxial Bi films are strongly influenced by the substrate compared with freestanding films. The substrate effects mainly include two aspects. First, the in-plane lattice constant of Bi(111) films is compressed, which increases the bandwidth of the surface-state-like bands. Furthermore, the band dispersion near the $\overline{\ensuremath{\Gamma}}$ point is significantly modified as well. Second, there exists a strong hybridization at the $\mathrm{Bi}/{\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ interface, and the hybridization effects spatially extend to three Bi bilayers.