Search results for "JUNCTION"
showing 10 items of 862 documents
Application of superconductor-semiconductor Schottky barrier for electron cooling
2003
Abstract Electronic cooling in superconductor–semiconductor–superconductor structures at sub kelvin temperatures has been demonstrated. Effect of the carrier concentration in the semiconductor on performance of the micro-cooler has been investigated.
Efficient Peltier refrigeration by a pair of normal metal/ insulator/superconductor junctions
1995
We suggest and demonstrate in experiment that two normal metal /insulator/ superconductor (NIS) tunnel junctions combined in series to form a symmetric SINIS structure can operate as an efficient Peltier refrigerator. Specifically, it is shown that the SINIS structure with normal-state junction resistances 1.0 and 1.1 k$\Omega$ is capable of reaching a temperature of about 100 mK starting from 300 mK. We estimate the corresponding cooling power to be 1.5 pW per total junction area of 0.8 $\mu$m$^2$ at $T= 300$ mK.
Trapping of quasiparticles of a nonequilibrium superconductor
2000
We have performed experiments where hot electrons are extracted from a normal metal into a superconductor through a tunnel junction. We have measured the cooling performance of such NIS junctions, especially in the cases where another normal metal electrode, a quasiparticle trap, is attached to the superconductor at different distances from the junction in direct metal-to-metal contact or through an oxide barrier. The direct contact at a submicron distance allows superior thermalization of the superconductor. We have analyzed theoretically the heat transport in this system. From both experiment and theory, it appears that NIS junctions can be used as refrigerators at low temperatures only w…
NIS chip refrigeration
1999
A normal-metal/insulator/superconductor (NIS) tunnel junction can be applied to cool electrons by biasing the junction suitably with external voltage. Two NIS junctions in series can form an efficient microrefrigerator because of the symmetry with bias voltage. Our SINIS microrefrigerator has been capable of reaching electronic temperatures of about 100 mK starting from 300 mK. To achieve appreciable refrigeration of the underlying lattice, the microrefrigerator must be thermally decoupled from the bulk substrate. We have demonstrated experimentally the reduction of lattice temperature by 23 mK at 180 mK by extending the normal electrode on a thin dielectric membrane with four suspended bri…
Spatially resolved measurement of nonequilibrium quasiparticle relaxation in superconducting Al
2011
Spatially resolved relaxation of nonequilibrium quasiparticles in a superconductor at ultralow temperatures was experimentally studied. It was found that the quasiparticle injection through a tunnel junction results in the modification of the shape of the I-V characteristic of a remote ``detector'' junction. The effect depends on the temperature, injection current, and proximity to the injector. The phenomena can be understood in terms of the creation of quasiparticle charge and energy disequilibrium characterized by two different length scales ${\ensuremath{\Lambda}}_{{Q}^{*}}~5$ and ${\ensuremath{\Lambda}}_{{T}^{*}}~40$ $\ensuremath{\mu}$m. The findings are in good agreement with existing…
Odd triplet superconductivity induced by the moving condensate
2020
It has been commonly accepted that magnetic field suppresses superconductivity by inducing the ordered motion of Cooper pairs. We demonstrate that magnetic field can instead provide a generation of superconducting correlations by inducing the motion of superconducting condensate. This effect arises in superconductor/ferromagnet heterostructures in the presence of Rashba spin-orbital coupling. We predict the odd-frequency spin-triplet superconducting correlations called the Berezinskii order to be switched on at large distances from the superconductor/ferromagnet interface by the application of a magnetic field. This is shown to result in the unusual behaviour of Josephson effect and local d…
Pac-Man Josephson junctions: Useful trigonometric puzzles?
2020
Abstract Rather interesting trigonometric equations arise when considering a Josephson junction obtained by embedding a Pac-Man shaped superconducting island in between two superconducting electrodes. In the present work we unfold these equations, written in terms of the superconducting phase difference between the two electrodes, and find the current-phase relation and the maximum superconducting current of the Josephson junction network. The solution of the trigonometric equations defining the superconducting current state of the system can be proposed to advanced high-school students or to undergraduate students in an interdisciplinary lecture.
Robust semi-Dirac points and unconventional topological phase transitions in doped superconducting Sr2IrO4 tunnel coupled to t2g electron systems
2017
Semi-Dirac fermions are known to exist at the critical points of topological phase transitions requiring fine-tuning of the parameters. We show that robust semi-Dirac points can appear in a heterostructure consisting of superconducting Sr2IrO4 and a t2g electron system (t2g-ES) without fine-tuning. They are topologically stable in the presence of the symmetries of the model, metallic t2g-ES and a single active band in Sr2IrO4. If the t2g metal is coupled to two different layers of Sr2IrO4 (effectively a multiband superconductor) in a three-layer-structure the semi-Dirac points can split into two stable Dirac points with opposite chiralities. A similar transition can be achieved if the t2g-E…
Heavy-fermion superconductivity induced by antiferromagnetic spin fluctuations
2007
Superconductivity is caused by an attractive interaction between electrons at the Fermi level that induces the pairing of time-reversed electron states to Cooper pairs. Conventionally this attractive interaction is mediated by phonons. Theoretically, non-phonon mediated coupling seems to be likely for heavy-fermion superconductors whose low-temperature dynamics is dominated by antiferromagnetic spin correlations. However, evidence for spin-fluctuation coupling has not yet been experimentally observed. One of the most direct methods of investigation of the superconducting state is tunneling spectroscopy. We prepared cross-type tunneling junctions composed of the heavy-fermion superconductor …
Josephson junctions and superconducting field effect transistors based on epitaxial Bi2Sr2Can-1CunO2(n+2) thin films
1998
Abstract Josephson junctions based on thin films of the Bi2Sr2Ca2Cu3O10+δ compound show IcRn products compatible with YBa2Cu3O7−δ samples. Using quasiparticle tunneling experiments we found evidence for a superconductor–insulator–superconductor tunneling process via localized states in the barrier. The Bi2Sr2CaCu2O8+δ compound is investigated regarding possible applications in superconducting field effect devices. We present thin films of four unit cells thickness that are superconducting at 58 K. An inverted metal–insulator–superconductor structure was prepared. From the modulation of the normal state resistance we estimate a carrier density of 7×1019 cm−3 for a superconducting sample. The…