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 Bi 2 Te 2 Se, Sb 2 Te 2 Se and Bi 2 Te 2 S 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 Bi 2 Te 2 Se and showed profound metallic nature in Sb 2 Te 2 Se and Bi 2 Te 2 S. We observed a bulk hole carrier concentration of 0.8 × 10 19 cm −3 through Hall coefficient study for the compound Sb 2 Te 2 Se, whereas Bi 2 Te 2 S exhibit an electron carrier density of 0.3 × 10 19  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.