Large magnetoresistance and quantum oscillations in Sn_0.05Pb_0.95Te

We have synthesized high-quality single crystals of Sn x Pb1-x Te and carried out detailed studies of the magnetotransport properties of one of the samples, Sn0.05Pb0.95Te. Longitudinal magnetoresistance increases almost linearly with increasing applied field (H) and reaches ∼310% at H = 13 T. At higher fields, both longitudinal and Hall resistance show clear Shubnikov de Haas oscillations. The oscillations are smooth and periodic, and there exists only one frequency, f α ∼ 57 T. However, an additional frequency, f β ∼ 69 T, appears as the angle between the field direction and the normal to the sample surface (θ) is increased. Both f α and f β exhibit θ-dependence; f α decreases whereas f β increases gradually with increasing θ. The presence of two frequencies in Sn0.05Pb0.95Te indicates that there exist two Fermi surface pockets (α and β pockets). We have constructed the Landau-level fan plot and determined the Berry phase (δ) for the α pocket to be δ ∼ 0.1. This δ value is very close to the expected value of 0 for a topologically trivial system.