Quantum oscillations and optical conductivity in Rashba spin-splitting BiTeI

We report the observation of Shubnikov--de Haas oscillations in single crystals of the Rashba spin-splitting compound BiTeI, from both longitudinal [Rₓₓ(B)] and Hall [Rxy(B)] magnetoresistance. Under magnetic fields up to 65 T, we resolved unambiguously only one frequency F=284.3±1.3 T, corresponding to a Fermi momentum kF=0.093±0.002 {}^-1. The amplitude of oscillations is strongly suppressed by a tilting magnetic field, suggesting a highly two-dimensional Fermi surface. Combining with optical spectroscopy, we show that quantum oscillations may be consistent with a bulk conduction band having a Rashba splitting momentum kR=0.046±0.0005 {}^-1.