15,866 research outputs found
Normal-Superfluid Interface Scattering For Polarized Fermion Gases
We argue that, for the recent experiments with imbalanced fermion gases, a
temperature difference may occur between the normal (N) and the gapped
superfluid (SF) phase. Using the mean-field formalism, we study particle
scattering off the N-SF interface from the deep BCS to the unitary regime. We
show that the thermal conductivity across the interface drops exponentially
fast with increasing , where is the chemical potential imbalance.
This implies a blocking of thermal equilibration between the N and the SF
phase. We also provide a possible mechanism for the creation of gap
oscillations (FFLO-like states) as seen in recent studies on these systems.Comment: 4 pages, 3 figure
Non local Andreev reflection in a carbon nanotube superconducting quantum interference device
We investigate a superconducting quantum interference device (SQUID) based on
carbon nanotubes in a fork geometry [J.-P. Cleuziou {\it et al.}, Nature
Nanotechnology {\bf 1}, 53 (2006)], involving tunneling of evanescent
quasiparticles through a superconductor over a distance comparable to the
superconducting coherence length, with therefore ``non local'' processes
generalizing non local Andreev reflection and elastic cotunneling. Non local
processes induce a reduction of the critical current and modify the
current-phase relation. We discuss arbitrary interface transparencies. Such
devices in fork geometries are candidates for probing the phase coherence of
crossed Andreev reflection.Comment: 13 pages, 8 figures, revised versio
Transport and spectroscopic properties of superconductor - ferromagnet - superconductor junctions of - -
Transport and Conductance spectra measurements of ramp-type junctions made of
cuprate superconducting electrodes and a manganite
ferromagnetic barrier are reported. At low
temperatures below , the conductance spectra show Andreev-like broad peaks
superposed on a tunneling-like background, and sometimes also sub-gap Andreev
resonances. The energy gap values found from fits of the data ranged
mostly between 7-10 mV. As usual, the gap features were suppressed under
magnetic fields but revealed the tunneling-like conductance background. After
field cycling to 5 or 6 T and back to 0 T, the conductance spectra were always
higher than under zero field cooling, reflecting the negative magnetoresistance
of the manganite barrier. A signature of superparamagnetism was found in the
conductance spectra of junctions with a 12 nm thick LCMO barrier. Observed
critical currents with barrier thickness of 12 nm or more, were shown to be an
artifact due to incomplete milling of one of the superconducting electrodes.Comment: 10 figure
- …