Structural and electronic transport properties of Zn- and Ga-doped Bi2-xSbxTe3-ySeytopological insulator single crystals.

ABSTRACT

A comprehensive study of structural and magnetotransport properties of pristine Bi2-xSbxTe3-ySey(BSTS) single crystals and doped with Zn (BSTSZn) and Ga (BSTSGa) are presented here. Magnetic field dependent Hall resistivities of the single crystals indicate that the holes are the majority carriers. The field dependent resistivity curves at different temperatures of the crystals display cusp-like characteristics at low magnetic fields, attributed to two-dimensional (2D) weak antilocalization (WAL) effect. We fit the observed low-field WAL effects at low temperatures using 2D and three-dimensional (3D) Hikami-Larkin-Nagaoka (HLN) equations. The 2D HLN equation fits the data more closely than the 3D HLN equation, indicating a 2D nature. The 2D HLN equation fit to the low field WAL effects at various temperatures reveal a phase coherence length (lφ) that decreases as temperature increases. The variation oflφwith temperature followsT-0.41power law for BSTSZn, suggesting that the dominant dephasing mechanism is a 2D electron-electron (e-e) interactions. For pristine BSTS and BSTSGa,lφ(T) is described by considering a coexistence of 2De-eand electron-phonon (e-p) interactions in the single crystals. The temperature variation of the longitudinal resistance in BSTSGa is described by 3D Mott variable range hoping model. In contrast, the transport mechanisms of both pristine BSTS and BSTSZn are described by a combination of 2D WAL/EEI models and 3D WAL.