419 research outputs found
Parity-Affected Persistent Currents in Superconducting Nanorings
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 -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
Statistics of Current Fluctuations and Electron-Electron Interactions in Mesoscopic Coherent Conductors
We formulate a general path integral approach which describes statistics of
current fluctuations in mesoscopic coherent conductors at arbitrary frequencies
and in the presence of interactions. Applying this approach to the
non-interacting case, we analyze the frequency dispersion of the third cumulant
of the current operator at frequencies well below both the inverse
charge relaxation time and the inverse electron dwell time. This dispersion
turns out to be important in the frequency range comparable to applied
voltages. For comparatively transparent conductors it may lead to the sign
change of . We also analyze the behavior of the second cumulant of
the current operator (current noise) in the presence of
electron-electron interactions. In a wide range of parameters we obtain
explicit universal dependencies of on temperature, voltage and
frequency. We demonstrate that Coulomb interaction decreases the Nyquist noise.
In this case the interaction correction to the noise spectrum is governed by
the combination , where is the transmission of the
-th conducting mode. The effect of electron-electron interactions on the
shot noise is more complicated. At sufficiently large voltages we recover two
different interaction corrections entering with opposite signs. The net result
is proportional to , i.e. Coulomb interaction
decreases the shot noise at low transmissions and increases it at high
transmissions.Comment: 12 pages, 3 figures. To be published in the Proceedings of the SPIE
Symposium on Fluctuations and Noise, Maspalomas, Grand Canaria, Spain (May
2004
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