85 research outputs found
Spectroscopy of SrRuO/Ru Junctions in Eutectic
We have investigated the tunnelling properties of the interface between
superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a
micro-fabrication technique, we have made Sr2RuO4/Ru junctions on the eutectic
system that consists of Sr2RuO4 and Ru micro-inclusions. Such a eutectic system
exhibits surface superconductivity, called the 3-K phase. A zero bias
conductance peak (ZBCP) was observed in the 3-K phase. We propose to use the
onset of the ZBCP to delineate the phase boundary of a time-reversal symmetry
breaking state.Comment: To be published in Proc of 24th Int. Conf. on Low Temperature Physics
(LT24); 2 page
A Cooper pair light emitting diode
We demonstrate Cooper-pair's drastic enhancement effect on band-to-band
radiative recombination in a semiconductor. Electron Cooper pairs injected from
a superconducting electrode into an active layer by the proximity effect
recombine with holes injected from a p-type electrode and dramatically
accelerate the photon generation rates of a light emitting diode in the
optical-fiber communication band. Cooper pairs are the condensation of
electrons at a spin-singlet quantum state and this condensation leads to the
observed enhancement of the electric-dipole transitions. Our results indicate
the possibility to open up new interdisciplinary fields between
superconductivity and optoelectronics.Comment: 5 pages (4 figures
Non-local Control of the Kondo Effect in a Double Quantum Dot-Quantum Wire Coupled System
We have performed low-temperature transport measurements on a double quantum
dot-quantum wire coupled device and demonstrated non-local control of the Kondo
effect in one dot by manipulating the electronic spin states of the other. We
discuss the modulation of the local density of states in the wire region due to
the Fano-Kondo antiresonance, and the Ruderman-Kittel-Kasuya-Yoshida (RKKY)
exchange interaction as the mechanisms responsible for the observed features.Comment: 4 pages, 4 figure
Observation of supercurrent enhancement in SNS junctions by non-equilibrium injection into supercurrent carrying bound Andreev states
We report for the first time enhancement of the supercurrent by means of
injection in a mesoscopic three terminal planar SNSNS device made of Al on
GaAs. When a current is injected from one of the superconducting Al electrodes
at an injection bias , the DC Josephson current between the
other two superconducting electrodes has a maximum, giving evidence for an
enhancement due to a non-equilibrium injection into bound Andreev states of the
underlying semiconductor. The effect persists to temperatures where the
equilibrium supercurrent has vanished.Comment: 7 pages + 3 figures. Resubmitted to Phys. Rev. Lett. Contents change
A superconducting-nanowire 3-terminal electronic device
In existing superconducting electronic systems, Josephson junctions play a
central role in processing and transmitting small-amplitude electrical signals.
However, Josephson-junction-based devices have a number of limitations
including: (1) sensitivity to magnetic fields, (2) limited gain, (3) inability
to drive large impedances, and (4) difficulty in controlling the junction
critical current (which depends sensitively on sub-Angstrom-scale thickness
variation of the tunneling barrier). Here we present a nanowire-based
superconducting electronic device, which we call the nanocryotron (nTron), that
does not rely on Josephson junctions and can be patterned from a single thin
film of superconducting material with conventional electron-beam lithography.
The nTron is a 3-terminal, T-shaped planar device with a gain of ~20 that is
capable of driving impedances of more than 100 k{\Omega}, and operates in
typical ambient magnetic fields at temperatures of 4.2K. The device uses a
localized, Joule-heated hotspot formed in the gate to modulate current flow in
a perpendicular superconducting channel. We have characterized the nTron,
matched it to a theoretical framework, and applied it both as a digital logic
element in a half-adder circuit, and as a digital amplifier for superconducting
nanowire single-photon detectors pulses. The nTron has immediate applications
in classical and quantum communications, photon sensing and astronomy, and its
performance characteristics make it compatible with existing superconducting
technologies. Furthermore, because the hotspot effect occurs in all known
superconductors, we expect the design to be extensible to other materials,
providing a path to digital logic, switching, and amplification in
high-temperature superconductors
InAs nanowire hot-electron Josephson transistor
At a superconductor (S)-normal metal (N) junction pairing correlations can
"leak-out" into the N region. This proximity effect [1, 2] modifies the system
transport properties and can lead to supercurrent flow in SNS junctions [3].
Recent experimental works showed the potential of semiconductor nanowires (NWs)
as building blocks for nanometre-scale devices [4-7], also in combination with
superconducting elements [8-12]. Here, we demonstrate an InAs NW Josephson
transistor where supercurrent is controlled by hot-quasiparticle injection from
normal-metal electrodes. Operational principle is based on the modification of
NW electron-energy distribution [13-20] that can yield reduced dissipation and
high-switching speed. We shall argue that exploitation of this principle with
heterostructured semiconductor NWs opens the way to a host of
out-of-equilibrium hybrid-nanodevice concepts [7, 21].Comment: 6 pages, 6 color figure
Evidence of two-electron tunneling interference in Nb/InAs junctions
The impact of junction transparency in driving phase-coherent charge transfer
across diffusive semiconductor-superconductor junctions is demonstrated. We
present conductivity data for a set of Nb-InAs junctions differing only in
interface transparency. Our experimental findings are analyzed within the
quasi-classical Green-function approach and unambiguously show the physical
processes giving rise to the observed excess zero-bias conductivity.Comment: 10 pages (RevTex), 4 figures (PostScript), accepted for pubblication
in Physical Review
Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions
We present a detailed study of nonequilibrium Josephson currents and
conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created
by means of quasiparticle injection from a normal reservoir connected to the
normal part of the junction. By applying a voltage at the normal reservoir the
Josephson current can be suppressed or the direction of the current can be
reversed. For a junction longer than the thermal length, , the
nonequilibrium current increases linearly with applied voltage, saturating at a
value equal to the equilibrium current of a short junction. The conductance
exhibits a finite bias anomaly around . For symmetric
injection, the conductance oscillates -periodically with the phase
difference between the superconductors, with position of the minimum
( or ) dependent on applied voltage and temperature. For
asymmetric injection, both the nonequilibrium Josephson current and the
conductance becomes -periodic in phase difference. Inclusion of barriers
at the NS-interfaces gives rise to a resonant behavior of the total Josephson
current with respect to junction length with a period . Both
three and four terminal junctions are studied.Comment: 21 pages, 19 figures, submitted to Phys. Rev.
PROCESSES OF IMPULSE BREAKDOWN IN N2-O2 GAS MIXTURES AND IN AIR AT LOW PRESSURE
No abstract availabl
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