We report a gate-tunable magnetoresistance and nonlinear Hall effect in thin ${\mathrm{Bi}}_y{\mathrm{Sb}}_{2-y}{\mathrm{Te}}_{3-x}{\mathrm{Se}}_x$ films grown by molecular beam epitaxy. The Hall coefficient $R_H$ exhibits distinct nonlinear behavior controlled by the gate voltage: a $\sim 2\%-3\%$ increase at low field ($B\sim 0.5\mathrm{T}$), opposite slopes for positive and negative gate biases at higher fields, and a substantial change at large negative gate voltages ($\sim -90\mathrm{V}$). Joint analysis of the gate dependences of magnetoresistance and the nonlinear Hall effect demonstrates a combined effect of topological surface states, trivial bulk states, holes in the inversion layer, and the smooth energy disorder, when the Fermi level is near the Dirac point. Because of the existence of several carrier groups, quantum corrections to the conductivity manifest themselves not only in the magnetoresistance, but also in the Hall effect. Our model quantitatively reproduces the gate dependence of both longitudinal and Hall resistances, allowing us to determine the concentrations and mobilities of all contributing carrier types.

Close

PrevNext

View figure in article

• Electrical properties
• Hall effect
• Quantum transport
• Surface states
• Topological insulators
• Topological materials