Unidirectional transmission of electrons in a magnetic field gradient

This work presents an experimental demonstration of time-reversal asymmetry of electron states propagating along the boundary separating areas with opposite magnetic fields. For this purpose we have fabricated a hybrid ferromagnet– semiconductor device in the form of a Hall cross with two ferromagnets deposited on top. The magnets generated two narrow magnetic barriers of opposite polarity in the active Hall area. We have observed that if the signs of the barriers are reversed, the bend resistance changes its sign. Using the Landauer–Büttiker theory, we have demonstrated that this is a direct consequence of asymmetric transmission of the “snake” and the “cycloidal” trajectories formed at the boundary separating the regions with opposite magnetic field directions.