Magnetoresistance and nonlinear Hall effect in quaternary topological insulator Bi1.5Sb0.5Te1.8Se1.2

The quaternary topological insulator Bi2−xSbxTe3−ySey has exhibited pronounced topological surface states with an insulating bulk. While most transport studies of these compounds are focused on thin flakes peeled from bulk crystals, we carefully analyzed the magneto transport properties of bulk Bi1.5Sb0.5Te1.8Se1.2. We have observed weak anti-localization (WAL) and nonlinear Hall effects at low temperatures. Using a multi-channel model, we decomposed the total conductance into three conducting channels of the bulk, impurity band and surface states at various temperatures. The conductance of the surface states is almost constant in the whole temperature range, and contributes about 19.1% in the total conductance at 1.9 K.