4,592 research outputs found
Frequency dependent third cumulant of current in diffusive conductors
We calculate the frequency dispersion of the third cumulant of current in
diffusive-metal contacts. The cumulant exhibits a dispersion at the inverse
time of diffusion across the contact, which is typically much smaller than the
inverse time. This dispersion is much more pronounced in the case of
strong electron-electron scattering than in the case of purely elastic
scattering because of a different symmetry of the relevant second-order
correlation functions.Comment: 8 pages, 4 figure
Current fluctuations near to the 2D superconductor-insulator quantum critical point
Systems near to quantum critical points show universal scaling in their
response functions. We consider whether this scaling is reflected in their
fluctuations; namely in current-noise. Naive scaling predicts low-temperature
Johnson noise crossing over to noise power at strong
electric fields. We study this crossover in the metallic state at the 2d z=1
superconductor/insulator quantum critical point. Using a Boltzmann-Langevin
approach within a 1/N-expansion, we show that the current noise obeys a scaling
form with . We recover
Johnson noise in thermal equilibrium and at strong
electric fields. The suppression from free carrier shot noise is due to strong
correlations at the critical point. We discuss its interpretation in terms of a
diverging carrier charge or as out-of-equilibrium Johnson
noise with effective temperature .Comment: 5 page
Divergence at low bias and down-mixing of the current noise in a diffusive superconductor-normal metal-superconductor junction
We present current noise measurements in a long diffusive
superconductor-normal-metal-superconductor junction in the low voltage regime,
in which transport can be partially described in terms of coherent multiple
Andreev reflections. We show that, when decreasing voltage, the current noise
exhibits a strong divergence together with a broad peak. We ascribe this peak
to the mixing between the ac- Josephson current and the noise of the junction
itself. We show that the junction noise corresponds to the thermal noise of a
nonlinear resistor 4kBT=R with R V = I V and no adjustable parameters
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