Inelastic helium atom scattering from Sb₂Te₃(111): phonon dispersion, focusing effects and surfing

Abstract

We present an experimental study of inelastic scattering processes on the (111) surface of the topological insulator Sb2Te3 using helium atom scattering. In contrast to other binary topological insulators such...

Measuring the Electron–Phonon Interaction in Two-Dimensional Superconductors with He-Atom Scattering

“…Inelastic HAS spectroscopy, besides measuring single surface phonon frequencies and the related λ Qν , allows for the observation of low-energy collective electronic excitations like phasons, amplitons and acoustic surface plasmons (ASP) [1,19,20,143] due to the direct "mechanical" interaction (Pauli repulsion) of He atoms with the surface electron density. When the ASP dispersion curve (linear in the long-wavelength limit [144]) enters the surface-projected phonon density, there are avoided crossings with the surface phonon dispersion curves and a robust renormalization of ASP phase velocity, all driven by e-ph interaction.…”

Material properties particularly suited to be measured with helium scattering: selected examples from 2D materials, van der Waals heterostructures, glassy materials, catalytic substrates, topological insulators and superconducting radio frequency materials

“…[151][152][153] Hence, HAS provides a sensitive probe to determine the surface phonon dispersion and energy dissipation processes in terms of the e-ph coupling constant, l, on the surfaces of these materials. The obtained experimental data of various TIs 92,145,[154][155][156][157][158][159] promise to evolve a more general picture about the surface dynamics and the atom-surface interaction of these peculiar surfaces. The e-ph coupling, as determined for several topological insulators belonging to the class of bismuth chalcogenides, suggests a dominant contribution of the surface quantum well states over the Dirac electrons in terms of l. 145 Investigations of the archetypal TI which is Bi 2 Te 3 (111) 155 show a prominent surface acoustic mode that may have important implications in layered and nanoscale devices.…”

Bulk band structure of Sb$_2$Te$_3$ determined by angle-resolved photoemission spectroscopy

“…When mapping the photoemission intensity at the Fermi level in two-dimensional k space, this band gives rise to six "flower petals" along Γ − M (this can be seen in Figure 2(a) in Ref. [27] using data taken from the same crystal as here at hν = 22 eV, and in Refs. [6,25]).…”

“…Sb 2 Te 3 crystals were grown following the procedure outlined in Ref. [27]. Attempts were made to synthesize bulk crystals with a smaller p-doping or to achieve chemical bulk counter-doping but these were not successful.…”