15/01/2009, 14:15, D5-153
Sergey Denisov, Universität Augsburg
I will start with a short introduction by using a simple model of an ac-driven particle in a periodic potential and discuss the main mechanisms of current rectification at the classical limit. I will then present results on the treatment of the quantum problem. For the coherent limit (when the system is decoupled from an external environment), the system dynamics is governed by a Floquet evolution matrix bearing the symmetry of the corresponding Hamiltonian. The dc-current appears due to the desymmetrization of Floquet eigenstates, which become transporting when all the relevant symmetries are violated. Finally I will discuss the quantum ratchet effect under the influence of a weak decoherence.