Dynamical Resonances and Stepped Current in an Attractive Quantum Pump

We report on the transport properties of a single mode quantum pump that operates by the simultaneous translation and oscillation of a potential well. We examine the dynamics comparatively using quantum, classical and semiclassical simulations. The use of an attractive or well potential is found to present several striking features absent if a barrier potential is used instead, as usually favored. The trapping of particles by the well for variable durations and subsequent release leads to a fractal-like structure in the distribution of the classical scattering trajectories. Interference among them leads to a rich dynamical structure in the quantum current, conspicuously missing in the classical current. Specifically, we observe sharp steps, spikes and dips in the current as a function of the incident energy of the carriers, and determine that a dynamical version of Fano resonance has a role that depends on the direction of incidence and on multiple scattering by the potential.