MESOSCOPIC DYNAMICAL ECHO IN QUANTUM DOTS

The time evolution of a wave packet within a disordered quantum dot is investigated. It is shown that although the disorder-averaged electron density is nearly homogeneous at times of the order of the diffusive time across the dot, at larger times there is a remarkable evolution towards a state with increasing correlation with the original state (i.e., an echo appears). At long times compared to the inverse mean level spacing the density distribution becomes time independent and preserves a memory of the original state. These effects are shown to reveal themselves in the relaxation of current through a quantum dot weakly coupled to reservoirs.