Magneto-optical evidence of the topological phase transition in (111)-Pb1-xSnxTe

Recently, the study of topological crystalline insulators has become of great interest in condensed matter physics. In this work, we present infrared magneto-optical investigation of such novel quantum states in narrow gap rocksalt IV-VI semiconductor Pb1-xSnxTe which exhibits a topological phase transition at a critical value x c≈0.40. High-mobility Bi-doped trivial and non-trivial (111)-Pb1-xSnxTe (0≤x≤0.56) films grown on BaF2 substrates by MBE were examined at 4.5K and magnetic fields B=0-15T. Massive and massless Dirac fermion models are used to analyze transmission spectra. We are able to determine the band parameters of the bulk and the topological surface states of such material.