Structural, magnetotransport and Hall coefficient studies in ternary Bi2Te2Se, Sb2Te2Se and Bi2Te2S tetradymite topological insulating compounds

Abstract

Temperature and magnetic field dependent resistivity studies of topological insulating materials Bi2Te2Se, Sb2Te2Se and Bi2Te2S are examined using various transport characteristics with suitable XRD and Raman structural analyses. The longitudinal resistivity data with decreasing of temperature reveals the insulating phase in Bi2Te2Se and showed profound metallic nature in Sb2Te2Se and Bi2Te2S. We observed a bulk hole carrier concentration of 0.8 × 1019 cm−3 through Hall coefficient study for the compound Sb2Te2Se, whereas Bi2Te2S exhibit an electron carrier density of 0.3 × 1019 cm−3 at 2 K and 9 T. Magnetoresistance results suggest a residual carrier effect from these polycrystalline topological compounds would degrade the actual experimental observation of surface state, instead, bulk insulating behaviour has been realized. With controllable bulk carrier effect, a single crystal approach may unleash the definite Dirac surface state with absence of impurity scattering over topological characteristics.