On the origin of nonreciprocal charge transport in topological insulator BiSbTeSe2

Nonreciprocal charge transport provides an effective approach for probing direction dependent charge dynamics and spin-momentum-locked electronic states. Here, we report highly gate-tunable nonreciprocal charge transport in dual-gated BiSbTeSe2 topological insulator device. The second-harmonic longitudinal resistance is linear in both current and magnetic field. The nonreciprocal response reaches its maximum near the charge neutrality point, exhibits sign reversals on either side, and is strongly suppressed once the Fermi level enters the bulk states. We suggest that the nonreciprocal response is attributed to the inhomogeneity of spin-momentum locking in the topological surface states. The nonreciprocal signal near the charge neutrality point is about one order of magnitude larger than that without gate modulation and remains robust up to 300 K, highlighting BiSbTeSe2 as a promising platform for room-temperature nonlinear electronics.