Determination of the surface states from the ultrafast electronic states in a thermoelectric material

We reveal the electronic structure in YbCd 2 Sb , a thermoelectric material, by angle-resolved photoemission spectroscopy (ARPES) and time-resolved ARPES (trARPES). Specifically, three bulk bands at vicinity of Fermi level are evidenced near Brillouin zone center, consistent with density functional theory (DFT) calculation. It is interesting that spin-unpolarized respond unexpectedly to right- left-handed circularly polarized probe. In addition, hole band surface states, which not sensitive polarization probe beam expected from DFT calculation, identified. find non-equilibrium quasiparticle recovery rate much smaller states than states. Our results demonstrate can be distinguished ones view time scale nonequilibrium physics.