Transport evidence of linear Dirac dispersion of non-trivial surface states in Fe-substituted PbBi2Te4 3D topological insulator

Abstract

Abstract We report here the experimental realization of Dirac Fermions in electronic transport measurements through observation of Shubnikov-de Haas (SdH) oscillations with π-Berry phase in PbBi2−xFexTe4 3D topological insulators . Substitution of magnetic impurity Fe 2+ for Bi3+ ions have tuned the Fermi level towards the Dirac point, evident from the Hall measurements as well as from the SdH oscillations. SdH oscillations of all the single crystals reveal the existence of non-trivial topological surface states along with an elongated band for x = 0 outside the surface states, associated with the π-Berry phase of the carriers, and is absent for doped specimens. The massless nature of the carriers having Fermi velocity ~105 ms−1depicts their relativistic nature. The carrier's effective mass are successfully tuned with successive Fe substitution, showing linear dependency on the Fermi wave vector; indicating the linear Dirac dispersion of topological surface states. The observed weak antilocalization fitted with modified Hikami-Larkin-Nagaoka (HLN) equation corroborates the 2D surface states in which the pseudo spin of the carriers move round the Dirac point acquires π-Berry phase and is consistent with the SdH oscillations.