123 research outputs found

    Quantum Decoherence in Disordered Mesoscopic Systems

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    We point out that the low temperature saturation of the electron phase decoherence time in a disordered conductor can be explained within the existing theory of weak localization provided the effect of quantum (high frequency) fluctuations is taken into account. Making use of the fluctuation-dissipation theorem we evaluate the quantum decoherence time, the crossover temperature below which thermal effects become unimportant, and the weak localization correction δσ\delta \sigma at T=0. For 1d systems the latter is found to be δσ1/N\delta \sigma \propto 1/ \sqrt{N}, where NN is the number of conducting channels.Comment: RevTeX, 3 page

    Parity-Affected Persistent Currents in Superconducting Nanorings

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    We argue that at sufficiently low temperatures T superconducting parity effect may strongly influence equilibrium persistent currents (PC) in isolated superconducting nanorings containing a weak link with few conducting modes. For a single channel quantum point contact at T=0 we predict a novel effect of parity-induced blocking of PC. In nanorings with SNS junctions a π\pi-state can occur for the odd number of electrons. Changing this number from even to odd yields spontaneous supercurrent in the ground state of such rings without any externally applied magnetic flux.Comment: Published versio