Vibrations in binary and ternary topological insulators: First-principles calculations and Raman spectroscopy measurements

Abstract

Density-functional perturbation theory and Raman spectroscopy are used in the study of vibrations in bulk V 2VI 3 binary and ternary topological insulators as well as in ultrathin films composed of one and two quintuple layers. Full dispersion curves along the Brillouin zone symmetry directions are calculated and analyzed and the zone-center Raman active modes are compared to the experimental results. The calculations of the two quintuple layer films reveal modes that correspond to displacements of entire quintuple layer blocks. These modes have low frequencies and are Raman active. The phonon dispersion curves of one and two quintuple layer Bi 2Se 3 films are compared with recent helium atom scattering experiments. © 2012 American Physical Society.