2,466 research outputs found
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
Huge nonequilibrium magnetoresistance in hybrid superconducting spin valves
A hybrid ferromagnet-superconductor spin valve is proposed. Its operation
relies on the interplay between nonequilibrium transport and proximity-induced
exchange coupling in superconductors. Huge tunnel magnetoresistance values as
large as some 10^6% can be achieved in suitable ferromagnet-superconductor
combinations under proper voltage biasing. The controllable spin-filter nature
of the structure combined with its intrinsic simplicity make this setup
attractive for low-temperature spintronic applications where reduced power
dissipation is an additional requirement.Comment: 4 pages, 4 figure
Ultra-low dissipation Josephson transistor
A superconductor-normal metal-superconductor (SNS) transistor based on
superconducting microcoolers is presented. The proposed 4-terminal device
consists of a long SNS Josephson junction whose N region is in addition
symmetrically connected to superconducting reservoirs through tunnel barriers
(I). Biasing the SINIS line allows to modify the quasiparticle temperature in
the weak link, thus controlling the Josephson current. We show that, in
suitable voltage and temperature regimes, large supercurrent enhancements can
be achieved with respect to equilibrium, due to electron ``cooling'' generated
by the control voltage. The extremely low power dissipation intrinsic to the
structure makes this device relevant for a number of electronic applications.Comment: 4 pages, 3 figures, to appear in Applied Physics Letter
Hybrid superconducting quantum magnetometer
A superconducting quantum magnetometer based on magnetic flux-driven
modulation of the density of states of a proximized metallic nanowire is
theoretically analyzed. With optimized geometrical and material parameters
transfer functions up to a few mV/Phi_0 and intrinsic flux noise ~10^{-9}Phi_0
Hz^{-1/2} below 1 K are achievable. The opportunity to access single-spin
detection joined with limited dissipation (of the order of ~ 10^{-14} W) make
this magnetometer interesting for the investigation of the switching dynamics
of molecules or individual magnetic nanoparticles.Comment: 6 pages, 6 color figures, added calculation of the Josephson current,
published versio
Mesoscopic supercurrent transistor controlled by nonequilibrium cooling
The distinctive quasiparticle distribution existing under nonequilibrium in a
superconductor-insulator-normal metal-insulator-superconductor (SINIS)
mesoscopic line is proposed as a novel tool to control the supercurrent
intensity in a long Josephson weak link. We present a description of this
system in the framework of the diffusive-limit quasiclassical Green-function
theory and take into account the effects of inelastic scattering with arbitrary
strength. Supercurrent enhancement and suppression, including a marked
transition to a -junction are striking features leading to a fully tunable
structure. The role of the degree of nonequilibrium, temperature, and materials
choice as well as features like noise, switching time, and current and power
gain are also addressed.Comment: 8 pages, 9 figures, submitted to Journal of Low Temperature Physic
Tailoring Josephson coupling through superconductivity-induced nonequilibrium
The distinctive quasiparticle distribution existing under nonequilibrium in a
superconductor-insulator-normal metal-insulator-superconductor (SINIS)
mesoscopic line is proposed as a novel tool to control the supercurrent
intensity in a long Josephson weak link. We present a description of this
system in the framework of the diffusive-limit quasiclassical Green-function
theory and take into account the effects of inelastic scattering with arbitrary
strength. Supercurrent enhancement and suppression, including a marked
transition to a -junction are striking features leading to a fully tunable
structure.Comment: 4 pages, 4 figure
Superconductors as ideal spin sources for spintronics
Spin-polarized transport is investigated in normal metal-superconductor (NS)
junctions as a function of interface transmissivity as well as temperature when
the density of states of a superconductor is Zeeman-split in response to an
exchange field (h_exc). Similarly to the "absolute spin-valve effect" predicted
by D. Huertas-Hernando et al. [Phys. Rev. Lett. 88, 047003 (2002)] in
superconducting proximity structures, we show that NS junctions can be used to
generate highly spin-polarized currents, in alternative to half-metallic
ferromagnets. In particular, the spin-polarized current obtained is largely
tunable in magnitude and sign by acting on bias voltage and h_exc. While for
tunnel contacts the current polarization can be as high as 100%, for
transparent junctions it is dominated by the minority spin species. The effect
can be enhanced by electron "cooling" provided by the superconducting gap.Comment: 4 pages, 4 color figures, published versio
Ultra-efficient Cooling in Ferromagnet-Superconductor Microrefrigerators
A promising scheme for electron microrefrigeration based on
ferromagnet-superconductor contacts is presented. In this setup, cooling power
densities up to 600 nW/m can be achieved leading to electronic
temperature reductions largely exceeding those obtained with existing
superconductor-normal metal tunnel contacts. Half-metallic CrO/Al bilayers
are indicated as ideal candidates for the implementation of the device.Comment: 9 pages, 3 figures, submitted to Applied Physics Letter
Crossed Andreev reflection-induced magnetoresistance
We show that very large negative magnetoresistance can be obtained in
magnetic trilayers in a current-in-plane geometry owing to the existence of
crossed Andreev reflection. This spin-valve consists of a thin superconducting
film sandwiched between two ferromagnetic layers whose magnetization is allowed
to be either parallelly or antiparallelly aligned. For a suitable choice of
structure parameters and nearly fully spin-polarized ferromagnets the
magnetoresistance can exceed -80%. Our results are relevant for the design and
implementation of spintronic devices exploiting ferromagnet-superconductor
structures.Comment: 5 pages, 4 figures, final published versio
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