Locking and unlocking of the counterflow transport in v= 1 quantum Hall bilayers by tilting of magnetic field

摘要

The counterflow transport in quantum Hall bilayers provided by superfluid excitons is locked at small input currents due to a complete leakage caused by the interlayer tunneling. We show that the counterflow critical current I~(CF) above which the system unlocks for the counterflow transport can be controlled by a tilt of magnetic field in the plane perpendicular to the current direction. The effect is asymmetric with respect to the tilting angle. The unlocking is accompanied by switching of the systems from the dc to the ac Josephson state. Similar switching takes place for the tunneling setup when the current flowing through the system exceeds the critical value I_c~T. At zero tilt the relation between the tunnel and counterflow critical currents is I_c~F=2I_c~(CF) . We compare the influence of the in-plane magnetic field component B_‖ on the critical currents I_c~(CF) and I_c~F. The in-plane magnetic field reduces the tunnel critical current and this reduction is symmetric with respect to the tilting angle. It is shown that the difference between I_c~(CF) and I_c~T is essential at field |B_‖| ≤φ_0/Dλ_J, where ?_0 is the flux quantum, d is the interlayer distance, and λ_J is the Josephson length. At larger B_‖ the critical currents I_c~(CF) and I_c~T almost coincide each other.