8,545 research outputs found
Nonlocal Cooper pair Splitting in a pSn Junction
Perfect Cooper pair splitting is proposed, based on crossed Andreev
reflection (CAR) in a p-type semiconductor - superconductor - n-type
semiconductor (pSn) junction. The ideal splitting is caused by the energy
filtering that is enforced by the bandstructure of the electrodes. The pSn
junction is modeled by the Bogoliubov-de Gennes equations and an extension of
the Blonder-Tinkham-Klapwijk theory beyond the Andreev approximation. Despite a
large momentum mismatch, the CAR current is predicted to be large. The proposed
straightforward experimental design and the 100% degree of pureness of the
nonlocal current open the way to pSn structures as high quality sources of
entanglement
Estimation of the particle-antiparticle correlation effect for pion production in heavy ion collisions
Estimation of the back-to-back pi-pi correlations arising due to evolution of
the pionic field in the course of pion production process is given for central
heavy nucleus collisions at moderate energies.Comment: 6 LaTeX pages + 5 ps figure
Crossed Andreev reflection in diffusive contacts
Crossed Andreev reflection in multiterminal structures in the diffusive
regime is addressed within the quasiclassical Keldysh-Usadel formalism. The
elastic cotunneling and crossed Andreev reflection of quasiparticles give
nonlocal currents and voltages (depending on the actual biasing of the devices)
by virtue of the induced proximity effect in the normal metal electrodes. The
magnitude of the nonlocal processes is found to scale with the square of the
barrier transparency and to decay exponentially with interface spacing.
Nonlocal cotunneling and crossed Andreev conductances are found to contribute
equally to the nonlocal current, which is of relevance to the use of normal
metal-superconducting heterostructures as sources of entanglement
Higher Order Bose-Einstein Correlations test the Gaussian Density Matrix Approach
A multiparticle system produced by a large number of independent sources is
described by a gaussian density matrix W. All theoretical approach to
Bose-Einstein Correlatios Cn in high energy physics use this form for W. One of
the most salient consequences of this form is the fact that all higher order
(n>2) moments of the current distribution can be expressed in terms of the
first two. We test this property by comparing the data on C2(Q^2), C3(Q^2) and
C4(Q^2) from pion-p and K-p reactions at 250 GeV/c with the predictions of a
general quantum statistical space-time approach. Even a simplified version of
such approach can account for the data. Previous attempts along these lines,
which did not use the space-time approach, met with difficulties.Comment: 17 pages (including one Table) and 2 figures. To appear in Physics
Letters B (PLB 13397
Two-photon correlations as a sign of sharp transition in quark-gluon plasma
The photon production arising due to time variation of the medium has been
considered. The Hamilton formalism for photons in time-variable medium (plasma)
has been developed with application to inclusive photon production. The results
have been used for calculation of the photon production in the course of
transition from quark-gluon phase to hadronic phase in relativistic heavy ion
collisions. The relative strength of the effect as well as specific two- photon
correlations have been evaluated. It has been demonstrated that the opposite
side two-photon correlations are indicative of the sharp transition from the
quark-gluon phase to hadrons.Comment: 23 pages, 2 figure
Fine structure of the local pseudogap and Fano effect for superconducting electrons near a zigzag graphene edge
Motivated by recent scanning tunneling experiments on zigzag-terminated
graphene this paper investigates an interplay of evanescent and extended
quasiparticle states in the local density of states (LDOS) near a zigzag edge
using the Green's function of the Dirac equation. A model system is considered
where the local electronic structure near the edge influences transport of both
normal and superconducting electrons via a Fano resonance. In particular, the
temperature enhancement of the critical Josephson current and 0-pi transitions
are predicted.Comment: 5 pages, 5 figures, to be published in Phys. Rev.
Andreev reflections on Y1-xCaxBa2Cu3O7-delta evidence for an unusual proximity effect
We have measured Andreev reflections between an Au tip and
Y_{1-x}Ca_{x}Ba_{2}Cu_{3}O_{7 - \delta} thin films in the in-plane orientation.
The conductance spectra are best fitted with a pair potential having the
"d_{x^{2}-y^{2}+is" symmetry. We find that the amplitude of the "is" component
is enhanced as the contact transparency is increased. This is an indication for
an unusual proximity effect that modifies the pair potential in the
superconductor near the surface with the normal metal.Comment: 4 pages, 4 figure
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