Detecting parity effect in a superconducting device in the presence of parity switches

AbstractKondo effect is an interesting phenomenon in quantum many-body physics. Niobium (Nb) is a conventional superconductor important for many superconducting device applications. It was long thought that the Kondo effect cannot be observed in Nb because the magnetic moment of a magnetic impurity, e.g. iron (Fe), would have been quenched in Nb. Here we report an observation of the Kondo effect in a Nb thin film structure. We found that by co-annealing Nb films with Fe in Argon gas at above 400 $$^{\circ }$$ ∘ C for an hour, one can induce a Kondo effect in Nb. The Kondo effect is more pronounced at higher annealing temperature. The temperature dependence of the resistance suggests existence of remnant superconductivity at low temperatures even though the system never becomes superconducting. We find that the Hamann theory for the Kondo resistivity gives a satisfactory fitting to the result. The Hamann analysis gives a Kondo temperature for this Nb–Fe system at $$\sim $$ ∼ 16 K, well above the superconducting transition onset temperature 9 K of the starting Nb film, suggesting that the screening of the impurity spins is effective to allow Cooper pairs to form at low temperatures. We suggest that the mechanism by which the Fe impurities retain partially their magnetic moment is that they are located at the grain boundaries, not fully dissolved into the bcc lattice of Nb.

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SPIN-PARITY EFFECT IN VIOLATION OF BELL'S INEQUALITIES

Modern Physics Letters B ◽

10.1142/s0217984914500043 ◽

2013 ◽

Vol 28 (01) ◽

pp. 1450004 ◽

Cited By ~ 4

Author(s):

ZHIGANG SONG ◽

J.-Q. LIANG ◽

L.-F. WEI

Keyword(s):

Berry Phase ◽

Quantum Probability ◽

Quantum Nonlocality ◽

Entangled State ◽

Bell’S Inequalities ◽

Bipartite Entanglement ◽

Spin Parity ◽

Parity Effect ◽

Bell's Inequalities ◽

Spin Parity Effect

Analytic formulas of Bell correlations are derived in terms of quantum probability statistics under the assumption of measuring outcome-independence and the Bell's inequalities (BIs) are extended to general bipartite-entanglement macroscopic quantum-states (MQS) of arbitrary spins. For a spin-½ entangled state we find analytically that the violations of BIs really resulted from the quantum nonlocal correlations. However, the BIs are always satisfied for the spin-1 entangled MQS. More generally the quantum nonlocality does not lead to the violation for the integer spins since the nonlocal interference effects cancel each other by the quantum statistical-average. Such a cancellation no longer exists for the half-integer spins due to the nontrivial Berry phase, and thus the violation of BIs is understood remarkably as an effect of geometric phase. Specifically, our generic observation of the spin-parity effect can be experimentally tested with the entangled photon-pairs.

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Nano-Strip Three-Terminal Superconducting Device for Cryogenic Detector Readout

IEEE Transactions on Applied Superconductivity ◽

10.1109/tasc.2010.2085411 ◽

2011 ◽

Vol 21 (3) ◽

pp. 717-720 ◽

Cited By ~ 9

Author(s):

Sergio Pagano ◽

Nadia Martucciello ◽

Roberto Cristiano ◽

Mikkel Ejrnaes ◽

Alessandro Casaburi ◽

...

Keyword(s):

Cryogenic Detector ◽

Superconducting Device

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Engineering of superconductors and superconducting devices using artificial pinning sites

Physical Sciences Reviews ◽

10.1515/psr-2017-8000 ◽

2017 ◽

Vol 2 (8) ◽

Cited By ~ 2

Author(s):

Roger Wördenweber

Keyword(s):

Superconducting Devices ◽

Basic Research ◽

Vortex State ◽

Superconducting Films ◽

Vortex Matter ◽

Superconducting Device ◽

New Concepts ◽

Basic Physics ◽

Power Handling Capability ◽

Device Properties

Abstract Vortex matter in superconducting films and devices is not only an interesting topic for basic research but plays a substantial role in the applications of superconductivity in general. We demonstrate, that in most electronic applications, magnetic flux penetrates the superconductor and affects the performance of superconducting devices. Therefore, vortex manipulation turns out to be a useful tool to avoid degradation of superconducting device properties. Moreover, it can also be used to analyze and understand novel and interesting physical properties and develop new concepts for superconductor applications. In this review, various concepts for vortex manipulation are sketched. For example, the use of micro- and nanopatterns (especially, antidots) for guiding and trapping of vortices in superconducting films and thin film devices is discussed and experimental evidence of their vortex guidance and vortex trapping by various arrangements of antidots is given. We demonstrate, that the vortex state of matter is very important in applications of superconductivity. A better understanding does not only lead to an improvement of the performance of superconductor components, such as reduced noise, better power handling capability, or improved reliability, it also promises deeper insight into the basic physics of vortices and vortex matter.

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