14,194 research outputs found
Non-local Andreev reflection under ac bias
We theoretically analyze non-local electron transport in multi-terminal
normal-metal-superconductor-normal-metal (NSN) devices in the presence of an
external ac voltage bias. Our analysis reveals a number of interesting effects,
such as, e.g., photon-assisted violation of balance between crossed Andreev
reflection (CAR) and elastic cotunneling (EC). We demonstrate that at
sufficiently small (typically subgap) frequencies of an external ac signal and
at low temperatures the non-local conductance of the NSN device turns negative
implying that in this regime CAR contribution to the non-local current
dominates over that of EC. Our predictions can be directly tested in future
experiments.Comment: published version, 6 pages, 3 figure
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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