Macroscopic quantum tunneling between Floqet cyclic states
Martin Heimsoth
Complutense University and Colorado School of Mines
Date: 03/28/2011
Abstract
The ratchet effect is the generation of asymptotic particle currents by exposing systems to
unbiased periodic driving fields. In the case of quantum mechanical systems the frequency of the
driving field has to be commensurate with the energy spectrum of the undriven system in order
to produce a resonant current. We present a simple and general scheme to predict these resonant
frequencies and the related asymptotic particle currents of Bose-Einstein-Condensates exposed to
a space and time-periodic potential with a weak driving amplitude. One of the main results of
this method is that in the resonant case only three Floquet cyclic states contribute to the
dynamics of the system. This three mode picture stays stable even when the particle interaction is
very strong. The equation describing the dynamical occupation of each mode reveals an analogy
of this system to a triple well system with macroscopic quantum tunneling, where the coupling
parameter between the wells can be tuned arbitrarily.