Persistent currents in nanorings and quantum decoherence by Coulomb interaction

Employing instanton technique we evaluate equilibrium persistent current (PC) produced by a quantum particle moving in a periodic potential on a ring and interacting with a dissipative environment formed by diffusive electron gas. The model allows for detailed nonperturbative analysis of interaction effects and, depending on the system parameters, yields a rich structure of different regimes. We demonstrate that at low temperatures PC is exponentially suppressed at sufficiently large ring perimeters 2 pi R>L-phi, where the dephasing length L-phi is set by interactions and does not depend on temperature. This behavior represents a clear example of quantum decoherence by electron-electron interactions at T -> 0.Employing instanton technique we evaluate equilibrium persistent current (PC) produced by a quantum particle moving in a periodic potential on a ring and interacting with a dissipative environment formed by diffusive electron gas. The model allows for detailed nonperturbative analysis of interaction effects and, depending on the system parameters, yields a rich structure of different regimes. We demonstrate that at low temperatures PC is exponentially suppressed at sufficiently large ring perimeters 2 pi R>L-phi, where the dephasing length L-phi is set by interactions and does not depend on temperature. This behavior represents a clear example of quantum decoherence by electron-electron interactions at T -> 0.