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Due to strong spin-orbit coupling and non-centrosymmetric crystal structure, the narrow band-gap semiconductor BiTeI hosts Rashba-split surface and bulk bands. This makes BiTeI a promising material for the generation of spin-polarized currents. It is intrinsically n-doped and exhibits additional strong band-bending at its polar surfaces, leading to partially occupied electron- and hole-like surface states for Te and I termination, respectively.
We studied the elecron and hole dynamics in the suface state and bulk conduction band on the Te-surface with time-resolved ARPES and observed a strong asymmetry for carriers close to the Fermi level. Electrons behave according to Fermi-liquid theory, while hole lifetimes decrease towards the Fermi level. We attribute this behavior to drift currents due to the surface band bending and the influence of a plasmon decay channel as predicted by Eremeev et al. in JETP Lett. 96, 437 (2012).
