Vortex ratchet effects in a superconducting asymmetric ring-shaped device

Abstract

We investigate the vortex ratchet effects in a superconducting asymmetric ring-shaped NbN device. Through transport measurements, we find that the rectified dc voltages are significantly enhanced, and we observe time-dependent asymmetric voltage waveforms over a single cycle. Our vortex ratchet device operates over a wide range of temperatures, critical currents, and magnetic fields. We demonstrate that in this asymmetric structure giant ratchet effects are mainly caused by the collective behavior of vortices, which differs clearly from one-particle vortex effects studied in conventional vortex ratchet systems.