1,060 research outputs found
Phase-dependent heat transport through magnetic Josephson tunnel junctions
We present an exhaustive study of the coherent heat transport through
superconductor-ferromagnet(S-F) Josephson junctions including a spin-filter
(I) tunneling barrier. By using the quasiclassical Keldysh Green's
function technique we derive a general expression for the heat current flowing
through a S/F/I/F/S junction and analyze the dependence of the thermal
conductance on the spin-filter efficiency, the phase difference between the
superconductors and the magnetization direction of the ferromagnetic layers. In
the case of non-collinear magnetizations we show explicitly the contributions
to the heat current stemming from the singlet and triplet components of the
superconducting condensate. We also demonstrate that the magnetothermal
resistance ratio of a S/F/I/F/S heat valve can be increased by the
spin-filter effect under suitable conditions.Comment: 8 pages; 6 figure
Manifestation of a spin-splitting field in a thermally-biased Josephson junction
We investigate the behavior of a Josephson junction consisting of a
ferromagnetic insulator-superconductor (FI-S) bilayer tunnel-coupled to a
superconducting electrode. We show that the Josephson coupling in the structure
is strenghtened by the presence of the spin-splitting field induced in the FI-S
bilayer. Such strenghtening manifests itself as an increase of the critical
current with the amplitude of the exchange field. Furthermore, the effect
can be strongly enhanced if the junction is taken out of equilibrium by a
temperature bias. We propose a realistic setup to assess experimentally the
magnitude of the induced exchange field, and predict a drastic deviation of the
curve ( is the temperature) with respect to equilibrium.Comment: 4.5 pages, 3 color figure
Quantum interference hybrid spin-current injector
We propose a quantum interference spin-injector nanodevice consisting of a
superconductor-normal metal hybrid loop connected to a
superconductor-ferromagnet bilayer via a tunneling junction. We show that for
certain values of the applied voltage bias across the tunnel barrier and the
magnetic flux through the loop the spin-current can be fully polarized.
Moreover, by tuning the magnetic flux one can switch the sign of the spin
polarization. This operation can be performed at frequencies within the tens of
GHz range. We explore the nanodevice in a wide range of parameters, establish
the optimum conditions for its experimental realization and discuss its
possible applications.Comment: 4.5 pages, 4 color figure
Properties of Mesoscopic Hybrid Superconducting Systems
In this paper we review several aspects of mesoscopic hybrid superconducting
systems. In particular we consider charge and heat transport properties in
hybrid superconducting-metal structures and the effect of charging energy in
superconducting nanostructures.Comment: 27 pages, 8 figure
Cooling electrons from 1 K to 400 mK with V-based nanorefrigerators
The fabrication and operation of V-based superconducting nanorefrigerators is
reported. Specifically, electrons in an Al island are cooled thanks to
hot-quasiparticle extraction provided by tunnel-coupled V electrodes.
Electronic temperature reduction down to 400 mK starting from 1 K is
demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3
micron^2. The present architecture extends to higher temperatures refrigeration
based on tunneling between superconductors and paves the way to the
implementation of a multi-stage on-chip cooling scheme operating from above 1 K
down to the mK regime.Comment: 3+ pages, 4 color figure
Josephson tunnel junction controlled by quasiparticle injection
A Josephson tunnel junction transistor based on quasiparticle injection is
proposed. Its operation relies on the manipulation of the electron distribution
in one of the junction electrodes. This is accomplished by injecting
quasiparticle current through the junction electrode by two additional tunnel
coupled superconductors. Both large supercurrent enhancement and fast quenching
can be achieved with respect to equilibrium by varying quasiparticle injection
for proper temperature regimes and suitable superconductor combinations. Joined
with large power gain this makes the device attractive for applications where
reduced noise and low power dissipation are required.Comment: 4 pages, 3 figure
Radiation comb generation with extended Josephson junctions
We propose the implementation of a Josephson radiation comb generator (JRCG)
based on an extended Josephson junction subject to a time dependent magnetic
field. The junction critical current shows known diffraction patterns and
determines the position of the critical nodes when it vanishes. When the
magnetic flux passes through one of such critical nodes, the superconducting
phase must undergo a -jump to minimize the Josephson energy.
Correspondingly a voltage pulse is generated at the extremes of the junction.
Under periodic driving this allows us to produce a comb-like voltage pulses
sequence. In the frequency domain it is possible to generate up to hundreds of
harmonics of the fundamental driving frequency, thus mimicking the frequency
comb used in optics and metrology. We discuss several implementations through a
rectangular, cylindrical and annular junction geometries, allowing us to
generate different radiation spectra and to produce an output power up to
~pW at ~GHz for a driving frequency of ~MHz.Comment: 4+ pages, 4 color figure
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