Electronic band structure of epitaxial PbTe (111) thin films observed by angle-resolved photoemission spectroscopy

Abstract

Using angle-resolved photoemission spectroscopy (ARPES), we studied bulk and surface electronic band structures of narrow-gap semiconductor lead telluride (PbTe) thin films grown by molecular beam epitaxy both perpendicular and parallel to the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}L$ direction. The comparison of ARPES data with the first-principles calculation reveals the details of band structures, orbital characters, spin-orbit splitting energies, and surface states. The photon-energy-dependent spectra show the bulk character. Both the $L$ and \ensuremath{\Sigma} valence bands are observed and their energy difference is determined. The spin-orbit splitting energies at $L$ and \ensuremath{\Gamma} points are 0.62 eV and 0.88 eV, respectively. The surface states below and close to the valence band maximum are identified. The valence bands are composed of a mixture of Pb $6s$ and Te 5 ${p}_{z}$ orbitals with dominant in-plane even parity, which is attributed to the layered distortion in the vicinity of the PbTe (111) surface. These findings provide insights into PbTe fundamental properties and shall benefit relevant thermoelectric and optoelectronic applications.