7,199 research outputs found
Current-phase relation of the SNS junction in a superconducting loop
We study the current-phase relation of the
superconductor/normal/superconductor (SNS) junction imbedded in a
superconducting loop. Considering the current conservation and free energy
minimum conditions, we obtain the persistent currents of the
normal/superconductor (NS) loop. At finite temperature we can explain the
experimentally observed highly non-sinusoidal currents which have maxima near
the zero external flux.Comment: 7 pages, 3 figures, version to appear in Europhys. Let
Thermal rectification of electrons in hybrid normal metal-superconductor nanojunctions
We theoretically investigate heat transport in hybrid normal
metal-superconductor (NS) nanojunctions focusing on the effect of thermal
rectification. We show that the heat diode effect in the junction strongly
depends on the transmissivity and the nature of the NS contact. Thermal
rectification efficiency can reach up to 123% for a fully-transmissive
ballistic junction and up to 84% in diffusive NS contacts. Both values exceed
the rectification efficiency of a NIS tunnel junction (I stands for an
insulator) by a factor close to 5 and 3, respectively. Furthermore, we show
that for NS point-contacts with low transmissivity, inversion of the heat diode
effect can take place. Our results could prove useful for tailoring heat
management at the nanoscale, and for mastering thermal flux propagation in
low-temperature caloritronic nanocircuitry.Comment: 4+ pages, 3 color figure
Relativistic transfer ionization and the Breit interaction
We consider correlated transfer ionization in relativistic collisions between
a highly charged ion and a light atom. In this process two quasi-free electrons
of the atom interact with each other during the short collision time that
results in capture of one of them by the ion and emission of the other. We show
that this process is strongly influenced by the generalized Breit interaction
already at modest relativistic impact energies.Comment: 5 pages, 4 figure
Density of states in d-wave superconductors of finite size
We consider the effect of the finite size in the ab-plane on the surface
density of states (DoS) in clean d-wave superconductors. In the bulk, the DoS
is gapless along the nodal directions, while the presence of a surface leads to
formation of another type of the low-energy states, the midgap states with zero
energy. We demonstrate that finiteness of the superconductor in one of
dimensions provides the energy gap for all directions of quasiparticle motion
except for \theta=45 degrees (\theta is the angle between the trajectory and
the surface normal); then the angle-averaged DoS behaves linearly at small
energies. This result is valid unless the crystal is 0- or 45-oriented (\alpha
\ne 0 or 45 degrees, where \alpha is the angle between the a-axis and the
surface normal). In the special case of \alpha=0, the spectrum is gapped for
all trajectories \theta; the angle-averaged DoS is also gapped. In the special
case of \alpha=45, the spectrum is gapless for all trajectories \theta; the
angle-averaged DoS is then large at low energies. In all the cases, the
angle-resolved DoS consists of energy bands that are formed similarly to the
Kronig-Penney model. The analytical results are confirmed by a self-consistent
numerical calculation.Comment: 9 pages (including 5 EPS figures), REVTeX
Spectrum of Andreev Bound States in a Molecule Embedded Inside a Microwave-Excited Superconducting Junction
Non-dissipative Josephson current through nanoscale superconducting
constrictions is carried by spectroscopically sharp energy states, so-called
Andreev bound states. Although theoretically predicted almost 40 years ago, no
direct spectroscopic evidence of these Andreev bound states exists to date. We
propose a novel type of spectroscopy based on embedding a superconducting
constriction, formed by a single-level molecule junction, in a microwave QED
cavity environment. In the electron-dressed cavity spectrum we find a polariton
excitation at twice the Andreev bound state energy, and a superconducting-phase
dependent ac Stark shift of the cavity frequency. Dispersive measurement of
this frequency shift can be used for Andreev bound state spectroscopy.Comment: Published version; 4+ pages, 3 figure
Fluctuations of the Josephson current and electron-electron interactions in superconducting weak links
We derive a microscopic effective action for superconducting contacts with
arbitrary transmission distribution of conducting channels. Provided
fluctuations of the Josephson phase remain sufficiently small our formalism
allows to fully describe fluctuation and interaction effects in such systems.
As compared to the well studied tunneling limit our analysis yields a number of
qualitatively new features which occur due to the presence of subgap Andreev
bound states in the system. We investigate the equilibrium supercurrent noise
and evaluate the electron-electron interaction correction to the Josephson
current across superconducting contacts. At T=0 this correction is found to
vanish for fully transparent contacts indicating the absence of Coulomb effects
in this limit.Comment: 12 pages, 4 figure
Supercurrent transferring through c-axis cuprate Josephson junctions with thick normal-metal-bridge
With simple but exactly solvable model, we investigate the supercurrent
transferring through the c-axis cuprate superconductor-normal
metal-superconductor junctions with the clean normal metal much thicker than
its coherence length. It is shown that the supercurrent as a function of
thickness of the normal metal decreases much slower than the exponential
decaying expected by the proximity effect. The present result may account for
the giant proximity effect observed in the c-axis cuprate SNS junctions.Comment: 6 pages, 4 figure
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