The topological surface state of $α$-Sn on InSb(001) as studied by
photoemission
arxiv Museu de Ciències Naturals de Barcelona
Authors:
MR Scholz, VA Rogalev, L Dudy, F Reis, F Adler, J Aulbach, LJ Collins-McIntyre, LB Duffy, HF Yang, YL Chen, T Hesjedal, ZK Liu, M Hoesch, S Muff, JH Dil, J Schäfer, R Claessen
Abstract:
We report on the electronic structure of the elemental topological semimetal
$\alpha$-Sn on InSb(001). High-resolution angle-resolved photoemission data
allow to observe the topological surface state (TSS) that is degenerate with
the bulk band structure and show that the former is unaffected by different
surface reconstructions. An unintentional $p$-type doping of the as-grown films
was compensated by deposition of potassium or tellurium after the growth,
thereby shifting the Dirac point of the surface state below the Fermi level. We
show that, while having the potential to break time-reversal symmetry, iron
impurities with a coverage of up to 0.25 monolayers do not have any further
impact on the surface state beyond that of K or Te. Furthermore, we have
measured the spin-momentum locking of electrons from the TSS by means of
spin-resolved photoemission. Our results show that the spin vector lies fully
in-plane, but it also has a finite radial component. Finally, we analyze the
decay of photoholes introduced in the photoemission process, and by this gain
insight into the many-body interactions in the system. Surprisingly, we extract
quasiparticle lifetimes comparable to other topological materials where the TSS
is located within a bulk band gap. We argue that the main decay of photoholes
is caused by intraband scattering, while scattering into bulk states is
suppressed due to different orbital symmetries of bulk and surface states.
