Discontinuous conductance of bichromatically ac-gated quantum wires

We study the electron transport through a quantum wire under the influence of external time-dependent gate voltages. The wire is modelled by a tight-binding Hamiltonian for which we obtain the current from the corresponding transmission. The numerical evaluation of the dc current reveals that for bichromatic driving, the conductance depends sensitively on the commensurability of the driving frequencies. The current even possesses a discontinuous frequency dependence. Moreover, we find that the conductance as a function of the wire length oscillates with a period that depends on the ratio between the driving frequencies.