PHASE BREAKING OF NONEQUILIBRIUM ELECTRONS IN A BALLISTIC QUANTUM-DOT

A study of phase breaking of equilibrium and nonequilibrium electrons in a ballistic quantum dot is presented. Estimates for the phase break ing time are obtained from the magnitude of the weak-localization peak , observed in the conductance on sweeping either magnetic held or de b ias voltage. These investigations reveal that the phase breaking of eq uilibrium and nonequilibrium electrons exhibits the same functional de pendence on energy. In particular, at sufficiently high energies the p hase breaking time is found to vary as an inverse square law of energy , consistent with predictions for electron-electron scattering due to Coulomb interaction in quantum dots. At lower energies, however, a sat uration in the phase breaking rate is observed, the onset of which is found to be well correlated to the average level spacing of the dot.