scholarly journals Controlling the proximity effect in a Co/Nb multilayer: the properties of electronic transport

2020 ◽  
Vol 11 ◽  
pp. 1336-1345 ◽  
Author(s):  
Sergey Bakurskiy ◽  
Mikhail Kupriyanov ◽  
Nikolay V Klenov ◽  
Igor Soloviev ◽  
Andrey Schegolev ◽  
...  
Keyword(s):  
Electronic Transport ◽  
Proximity Effect ◽  
Superconducting Order Parameter ◽  
Experimental Investigations ◽  
Resistive Transition ◽  
Local Magnetization ◽  
Ferromagnetic Layers ◽  
Magnetization Orientation ◽  
Usadel Equations ◽  
A Current

We present both theoretical and experimental investigations of the proximity effect in a stack-like superconductor/ferromagnetic (S/F) superlattice, where ferromagnetic layers with different thicknesses and coercive fields are made of Co. Calculations based on the Usadel equations allow us to find the conditions at which switching from the parallel to the antiparallel alignment of the neighboring F-layers leads to a significant change of the superconducting order parameter in superconductive thin films. We experimentally study the transport properties of a lithographically patterned Nb/Co multilayer. We observe that the resistive transition of the multilayer structure has multiple steps, which we attribute to the transition of individual superconductive layers with the critical temperature, T c, depending on the local magnetization orientation of the neighboring F-layers. We argue that such superlattices can be used as tunable kinetic inductors designed for artificial neural networks representing the information in a “current domain”.

scholarly journals Controlling the proximity in a Co/Nb multilayer: the properties of electronic transport

2020 ◽  
Author(s):  
Sergey Bakurskiy ◽  
Mikhail Kupriyanov ◽  
Nikolay V Klenov ◽  
Igor Soloviev ◽  
Andrey Schegolev ◽  
...  
Keyword(s):  
Neural Networks ◽  
Electronic Transport ◽  
Proximity Effect ◽  
Order Parameter ◽  
Superconducting Order Parameter ◽  
Resistive Transition ◽  
Local Magnetization ◽  
Ferromagnetic Layers ◽  
Magnetization Orientation ◽  
Usadel Equations

We present both a theoretical and experimental investigation of the proximity effect in a stack-like superconductor/ferromagnet (S/F) superlattice, where ferromagnetic layers with different thicknesses and coercive fields are made of Co. Calculations based on Usadel equations allow us to find conditions at which switching from the parallel to the antiparallel alignment of neighboring F-layers leads to a significant change of the superconducting order parameter in thin s-films. Experimentally we study the transport properties of a lithographically patterned Nb/Co multilayer. We observe that the resistive transition of the multilayer contains multiple steps, which we attribute to the transition of individual s-layers with T c’s depending on the local magnetization orientation of neighbor F-layers. We argue that such superlattices can be used as tunable kinetic inductors, designed for artificial neural networks with a representation of information in the current domain.

scholarly journals Superconducting Order Parameter Nucleation and Critical Currents in the Presence of Weak Stray Fields in Superconductor/Insulator/Ferromagnet Hybrids

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 507
Author(s):  
Vasiliy N. Kushnir ◽  
Serghej L. Prischepa ◽  
Michela Trezza ◽  
Carla Cirillo ◽  
Carmine Attanasio
Keyword(s):  
Phenomenological Theory ◽  
Critical Currents ◽  
Superconducting Phase ◽  
Stray Field ◽  
Superconducting Properties ◽  
Ginzburg Landau ◽  
Ferromagnetic Layers ◽  
Linearized System ◽  
Critical Current Density Jc ◽  
Usadel Equations

The stray fields produced by ferromagnetic layers in Superconductor/Insulator/Ferromagnet (S/I/F) heterostructures may strongly influence their superconducting properties. Suitable magnetic configurations can be exploited to manipulate the main parameters of the hybrids. Here, the nucleation of the superconducting phase in an external magnetic field that periodically oscillates along the film width is studied on the base of the numerical solution of the linearized system of Usadel equations. In addition, the effect of the magnetic configuration of the F-layer on the temperature dependence of the critical current density, Jc(T), is investigated in the framework of the Ginzburg–Landau phenomenological theory on the base of the oscillating model of a stray field. By following this approach, the Jc(T) dependence of a Nb/SiO2/PdNi trilayer is reproduced for different magnetic configurations of the PdNi layer.

scholarly journals Electric readout of magnetic stripes in insulators

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yao Chen ◽  
Yuki Shiomi ◽  
Zhiyong Qiu ◽  
Tomohiko Niizeki ◽  
Maki Umeda ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Field Resistance ◽  
Superconducting Order Parameter ◽  
Nanometer Scale ◽  
Zero Field ◽  
Local Magnetization ◽  
Resistance Change ◽  
Analog Memory ◽  
Superconductor Film ◽  
Topological Configuration

AbstractIn superconductors, a topological configuration of the superconducting order parameter called a superconducting vortex carries magnetization. Such a magnetic topological object behaves like a minute particle generating a magnetic flux. Since the flux is localized with a nanometer scale, the vortex provides a nano-scale probe for local magnetic fields. Here we show that information of magnetic stripes in insulators can be read out by using vortices in an adjacent superconductor film as a probe. The orientation and width of magnetic micro stripes are both transcribed into resistance change of the superconductor through the modulation of vortex mobility affected by local magnetization. By changing the direction of external magnetic fields, zero-field resistance changes continuously according to the stripe orientation, and its modulation magnitude reaches up to 100%. The width of the stripes can also be estimated from the oscillatory magnetoresistance. Our results demonstrate a new possibility for non-volatile analog memory devices based on topological objects.

Numerical and Experimental Investigations of Wave Field Around a Circular Island with the Presence of Weak Currents

2002 ◽  
Vol 18 (1) ◽  
pp. 35-42
Author(s):  
Ming-Chung Lin ◽  
Chao-Min Hsu ◽  
Shou-Cheng Wang ◽  
Chao-Lung Ting
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Height ◽  
Incident Wave ◽  
Numerical Calculations ◽  
Experimental Investigations ◽  
Wave Refraction ◽  
Circular Island ◽  
Incident Waves ◽  
A Current

ABSTRACTThis study elucidated the complicated phenomena of wave refraction and diffraction around a circular island due to random incident waves traveling with a current. Various combinations of random incident wave and current conditions were used to investigate the wave height distributions around a circular island numerically and experimentally. Numerical calculations were carried out based on the theory derived by Lin & Hsu [1]. According to the results, it shows that numerical calculations can predict experimental data quantitatively well.

scholarly journals Free coherent evolution of a coupled atomic spin system initialized by electron scattering

Science ◽  
2021 ◽  
Vol 372 (6545) ◽  
pp. 964-968
Author(s):  
Lukas M. Veldman ◽  
Laëtitia Farinacci ◽  
Rasa Rejali ◽  
Rik Broekhoven ◽  
Jérémie Gobeil ◽  
...  
Keyword(s):  
Magnetic Interaction ◽  
Scanning Tunneling ◽  
Local Magnetization ◽  
Tunneling Microscopy ◽  
Pump Probe ◽  
Atomic Spin ◽  
Spin Lattice ◽  
Atomic Spins ◽  
Insight Into ◽  
A Current

Full insight into the dynamics of a coupled quantum system depends on the ability to follow the effect of a local excitation in real-time. Here, we trace the free coherent evolution of a pair of coupled atomic spins by means of scanning tunneling microscopy. Rather than using microwave pulses, we use a direct-current pump-probe scheme to detect the local magnetization after a current-induced excitation performed on one of the spins. By making use of magnetic interaction with the probe tip, we are able to tune the relative precession of the spins. We show that only if their Larmor frequencies match, the two spins can entangle, causing angular momentum to be swapped back and forth. These results provide insight into the locality of electron spin scattering and set the stage for controlled migration of a quantum state through an extended spin lattice.

scholarly journals Current Fluctuations in Hybrid-Superconductor Normal Structures with Quantum Dots

2021 ◽  
Author(s):  
◽  
Stephanie Droste
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Electronic Transport ◽  
Proximity Effect ◽  
Noise Spectrum ◽  
Current Fluctuations ◽  
Cooper Pairs ◽  
Finite Frequency ◽  
Strong Coulomb ◽  
Superconducting Correlations

<p>Nanostructures with quantum dots in proximity to superconducting electrodes are an ideal tool to study superconducting correlations in systems with few degrees of freedom that exhibit strong Coulomb-interaction effects. Such hybrid superconductor-normal structures show rich physics due to the interplay of superconductivity, Coulomb interaction and non-equilibrium. Superconducting correlations are established on the quantum dot when it is coupled to a superconductor even in the presence of strong Coulomb repulsion and Cooper pairs can tunnel coherently between the quantum dot and the superconductor.  In this thesis, we investigate theoretically electronic transport through an interacting quantum dot coupled to normal and superconducting leads. The presence of the proximity effect can be detected by the dot's current, namely the Andreev current. However, current fluctuations might reveal information on the electronic transport and the internal structure of the system which is not visible in the mean value of the current. For this reason, we study the current fluctuations through the proximized quantum dot to get access to the properties of such a hybrid quantum-dot system. In particular, we are interested in the finite-frequency fluctuations to unveil the coherent dynamics underlying the proximity effect in the quantum dot and its internal time scales.  At first, we present a study of the frequency-dependent current noise for subgap transport through an interacting single-level quantum dot tunnel-coupled to normal and superconducting leads. For this purpose, we employ a non-equilibrium diagrammatic real-time approach to calculate the finite-frequency current noise. The finite-frequency noise spectrum shows a sharp dip at a frequency corresponding to the energy splitting of the Andreev bound states which is a signature of the coherent exchange of Cooper pairs between the quantum dot and the superconductor. Furthermore, in the high frequency regime, the so called quantum noise regime, the noise spectrum exhibits steps at frequencies equal to the excitation energies. These steps can be related to the effective coupling strength of the excitations.  However, the statistical description of the electron transport does not stop with the noise. Current cumulants of arbitrary order can be obtained by means of full counting statistics (FCS). We set up a theory based on the diagrammatic real-time approach to calculate the finite-time FCS for quantum transport with a non-Markovian master equation that captures the initial correlations between system and reservoir. This allows us to fully describe the current fluctuations of the hybrid quantum-dot system, that is the noise and all higher order current cumulants.</p>

Dynamics of a Current Collector for a High-Speed Railway

1975 ◽  
Vol 97 (2) ◽  
pp. 731-738
Author(s):  
Kazuo Yoshida ◽  
Katsushi Manabe ◽  
Taro Shimogo
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Current Collector ◽  
Experimental Investigations ◽  
High Speed Railway ◽  
Collector System ◽  
Train Speed ◽  
Proper Values ◽  
Very High ◽  
A Current

In this paper, a mathematical model of a collecting rail and collector system with sliding contactors is proposed for a current collector system of a very-high-speed railway. Its dynamic characteristics, especially the variation of contact force and the probability of contact break, are investigated by means of linear analysis. In order to prove the appropriateness of the linear model, the computer simulation and theoretical analysis are performed using a nonlinear model. Experimental investigations are also performed in order to examine the dynamic characteristics of the model. From these results, it is concluded that the probability of contact break can be kept to less than about 10 percent for a train speed of 500 km/hr by choosing the proper values of natural frequencies and damping ratios under constraints.

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