Atom-surface van der Waals potentials of topological insulators and semimetals from scattering measurements

Abstract

Gas-surface scattering experiments yield high accuracy interaction potentials in the van der Waals regime. A perspective overview for topological semimetals & insulators is provided and the importance for benchmarking ab initio calculations outlined.

Motion of water monomers reveals a kinetic barrier to ice nucleation on graphene

“…For example, on graphene, water has previously only been visualised when subsurface, due to its dynamic nature 61 , 62 . Compared with other techniques, He atom scattering has the advantage of being the most delicate surface-probing technique and is sensitive to H atoms in the top layer 63 – 66 . All measurements have therefore been performed using the Cambridge helium-3 spin-echo facility (HeSE) 27 , 67 , 68 .…”

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

“…Thus, a surface probe such as He atoms with incident energies in the range of tens of meV that only tickle the surface where the electron density is ~10 −4 a.u. [8], can even measure the dispersion curves of phonons propagating at several atomic planes beneath the surface (quantum sonar effect), e.g., at the interface of ultra-thin metal films with the substrate, provided the e-ph coupling is sufficiently strong [7,9].…”

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.…”

“…An article describing in detail the methods for obtaining atom-surface interaction potentials from HAS experiments can be found as part of this special issue. 92 It is appropriate to compare the capabilities of HAS to the standard tools for measuring nanoscale topography: Scanning Tunnelling Microscopy (STM) and Atomic Force Microscopy (AFM). Firstly it should be noted that both of these techniques are obviously more versatile than HAS because they provide real space images and thus do not require the investigated samples to contain periodic features.…”