Planar Hall Effect In A Bulk Topological Insulator Sn Doped Bi_1.1Sb_0.9Te₂S

A topological insulator is a narrow-band-gap insulator with two-dimensional massless Dirac Fermions on its surfaces.Due to the protection of time reversal symmetry,Dirac Fermions exhibit a linearly dispersive band structure and a particular spin-momentum locking behavior,which ensures a back-scattering forbidden feature against the nonmagnetic impurities.Two important areas in three dimensional topological insulators research are the growth of high-quality bulk-insulating topological insulator single crystals and the study of the properties of Dirac Fermions.In this work,the high-quality Sn-doped Bi1.1Sb0.9Te2S single crystals are prepared by a controlled melting method.The Dirac cone structure is observed by Angle resolved photoemission spectroscopy,which Dirac point is about 126 meV below the Fermi level.The transport properties of the samples are measured systematically.It is found that Sn-doped Bi1.1Sb0.9Te2S is a bulk insulator attaining tens of ?cm at the low temperature.Through the analysis of Shubnikov-de Haas oscillation,the two-dimensional nontrivial topological surface states dominate the transport at low temperatures,which have a quite low carrier concentrationFurthermore,we observe the planar Hall effect in bulk single crystals for the first time,showing a sin 20 angle-dependent relationship.With the increasing temperature,the amplitude of planar Hall resistance decrease obviously from 100 K to 150 K.This decrease is due to the transition from planar Hall effect to tradition Hall effect by analyzing the data.