DOCSLIB.ORG

Magnetic Flux Pumping in Superconducting Loop Containing a Josephson Ψ Junction S

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Magnetic Flux Pumping in Superconducting Loop Containing a Josephson Ψ Junction S Magnetic Flux Pumping in Superconducting Loop Containing a Josephson Junction S. Mironov,1 H. Meng,2, 3, 4 and A. Buzdin2, 5 1)Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod, Russia 2)University Bordeaux, LOMA UMR-CNRS 5798, F-33405 Talence Cedex, France 3)School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001, China 4)Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444, China 5)Sechenov First Moscow State Medical University, Moscow, 119991, Russia We demonstrate that a Josephson junction with a half-metallic weak link integrated into the superconducting loop enables the pumping of magnetic flux piercing the loop. In such junctions the ground state phase is determined by the mutual orientation of magnetic moments in two ferromagnets surrounding the half-metal. Thus, the precession of magnetic moment in one of two ferromagnets controlled, e.g., by the microwave radiation, results in the accumulation of the phase and subsequent switching between the states with different vorticities. The proposed flux pumping mechanism does not require the application of voltage or external magnetic field which enables the design of electrically decoupled memory cells in superconducting spintronics. When a superconducting loop is put in the external magnetic field the magnetic flux Φ through the loop is B~ quantized being equal to the integer number of the flux 1 quanta Φ0: Φ = nΦ0 . The interplay between the states with different vorticities n enables the implementation of multiply connected superconducting systems as flux qubits2,3, ultra-sensitive magnetic field detectors4,5, gen- erators of ac radiation6 etc. The flux quantization also Controllable Energy naturally suggests using superconducting loop as topo- switching logically protected memory cell in the devices of the rapid single flux quantum (RSFQ) logics7. The straightforward way to switch the loop between the states with different vorticity n requires application of external magnetic flux Φ ∼ Φ . Even for the loops -1 0 1 ext 0 Φ / Φ of the radius R ∼ 0:1 µm the corresponding magnetic 0 field should be ∼ 0:1 T and it grows / R−2 with the de- crease of the loop size which becomes a serious obstacle FIG. 1. Sketch of the superconducting loop containing a for the miniaturization of the flux-based devices. Thus, Josephson junction which enables the switching between the discovery of the physical phenomena which enable the states with different vorticities by periodic driving of the ground state Josephson phase . the controllable switching of the vorticity n without ap- plication of external flux is strongly desired. One of promising mechanisms allowing the flux- free switching can be realized in the loops containing different vorticity without application of external mag- a Josephson junction with embedded magnetic order netic field. 8{11 and/or broken inversion symmetry . These systems However, in most existing '0 junctions the phase vari- are known to reveal unusual collective dynamics of mag- ation is limited (δ'0 < 2π) and the corresponding flux 12{19 netic and superconducting order parameters. In con- Φ < Φ0 cannot change the vorticity n of the supercon- arXiv:2004.13403v1 [cond-mat.supr-con] 28 Apr 2020 trast to the conventional Josephson systems, such junc- ducting state. Indeed, the junctions with a ferromagnetic tions support the non-zero ground state phase '0 be- (F) layer between the superconducting (S) leads support 25{27 tween the superconducting leads. Being incorporated only π states with '0 = π which allow the design 23 into the loop such '0-junctions play the role of the phase of the environmentally decoupled qubits but are not batteries producing the spontaneous electric current suitable for changing the loop vorticity. The alternat- which corresponds to the magnetic flux Φ = ('0=2π)Φ0 ing F layer thickness (see, e.g., Ref. 28 and references through the loop20{24. One can expect, thus, that con- therein) as well as the presence of the Abrikosov vortex 30{32 trolling the ground state phase '0, e.g., by voltage or or the pair of current injectors in one of S leads may radiation should enable effective tuning of the magnetic produce the second order phase transition with the spon- flux and switching the system between the states with taneous phase '0 gradually changing between zero and 2 FIG. 2. (a) Sketch of the Josephson junction where the weak link consists of a half-metallic layer sandwiched between two ferromagnets. The ground state phase coincides with the angle between the projection of magnetic moments in ferromagnets to the plane perpendicular to the spin quantization axis of half-metal. (b) Sketch of possible experimental setup where circularly polarized radiation controls the rotation of magnetic moment in the F2 layer and subsequent variation of the spontaneous Josephson phase . The superconducting electrodes are covered by the reflecting material to minimize heating effects. π (so that δ'0 < π). The situation looks more promis- netic field. ing for the the S/F/S junctions with the broken inversion The described phase accumulation in junctions re- symmetry where the spin-orbit coupling (SOC) produces minds the Berry phase effect45 since the full recovery of the arbitrary spontaneous phase '0 / ν sin θ where θ the initial magnetic state after the one precession period is the angle between the exchange field in the F mate- is accompanied by the 2π change of the Josephson ground rial and the direction of the broken inversion symmetry state phase . Note that this phenomenon contrasts to while the constant ν characterizes the strength of SOC the behavior of the '0 junctions where the recovery of the and the exchange field33{37. However, the parameter ν is exchange field direction (the angle θ) unavoidably results typically small which limits the '0 variations. in the recovery of the spontaneous phase '0 / sin θ. In this Letter we unravel the flux-free mechanism of For the experimental realization of the described the remote control of the superconducting state vortic- radiation-stimulated vorticity switching it is convenient ity in the loop by the Josephson junction in which to use the Josephson junctions of the \overlap" ge- the range of the spontaneous phase variation is not ometry (see Fig. 2b). This design provides a convenient limited (see Fig. 1). The weak link of the basic junc- access to the surface of the F2 layer for the circularly tion consists of the layer of half-metal (HM) sandwiched polarized electromagnetic wave. At the same time, the between two ferromagnets (Fig. 2a). If the magnetic superconducting electrodes should be covered by the suit- moments in the three magnetic layers are non-coplanar able reflecting material to prevent parasitic heating ef- the current-phase relation of the junction takes the form fects. The recent experiments have demonstrated the active control of triplet supercurrents in different types I(') = Ic sin(' − ) where the spontaneous phase and 46{50 the critical current I are controlled by the directions of of S/F/S junctions including the Josepshon systems c with half-metallic layers.51,52 which provides the guid- the magnetic moments M1 and M2 in the F1 and F2 layers. Specifically, for the spin quantization axis in the ance for the appropriate choice of materials and their half-metal directed along the z-axis the phase coincides parameters. To demonstrate the controllable switching of vorticity with the angle between the projection of M1 and M2 to the xy-plane while the critical current I / sin α sin α and the magnetic flux pumping we consider the supercon- c 1 2 ducting loop of inductance L interrupted by the Joseph- where α1 (α2) is the angle between M1 (M2) and the z- axis.38{43. The geometry of the junction favorable for son junction characterized by the the current-phase the control of the loop vorticity requires the direction of relation I = Ic sin(' − ) where Ic is the critical current (see Fig. 1). The dynamics of the Josephson phase ' is M1 to be fixed along the y-axis and the F2 layer to have 1 the easy-plane (xy) magnetic anisotropy. In this case described by the sine-Gordon equation : radiating the F layer with the circularly polarized elec- 2 2 @ ' 1 @' 1 2πIc tromagnetic wave with the magnetic field rotating in the 2 + + ' + sin [' − (t)] = 0; (1) @t RN C @t LC Φ0C xy plane should cause the precession of M2 around the 44 z-axis resulting in the unlimited accumulation of the where C and RN are the capacity and normal state resis- spontaneous phase . If the described junction is inte- tance of the Josephson junction, respectively. Consider- grated in the superconducting loop such phase accumu- ing the case of identical easy-axis anisotropy of magneti- lation gives rise to the switching between the states with zation in both F layers of the junction we assume that different vorticities and subsequent pumping of magnetic in the absence of external driving (t) = 0. To analyze flux through the loop without actual application of mag- the system dynamics it is convenient to introduce the di- 3 p mensionless time τ = !pt where !p = 2πIc=Φ0C is the p plasma frequency, the quality factor Q = R 2πIcC=Φ0 2 (a) Stable state sin ϕ and the normalized loop inductance λ = 2πLIc=Φ0. In the absence of external driving the number of equi- 0 librium superconducting states in the loop is controlled Saddle −ϕ/λ by the loop inductance. At small λ the equation sin ' = -2 point −ϕ/λ defining the equilibrium states has only one triv- -6 -4 -2 0 2 4 6 ial solution ' = 0. When increasing λ at the threshold ϕ/π values λ = λn one gets the sequential emergence of addi- tional pairs of the stable states ' = ±'n (n = 1; 2; 3:::) 2 (b) sdl and the nearby saddle points ' = ±'n (see Fig.
Load more

Recommended publications
  • Design and Characterization of a LTS Flux Pump System for Possible
    University of Groningen Bachelor Thesis in Physics Research performed at SRON Design and characterization of a LTS flux pump system for possible satellite application Supervisor: Author: dr. ir. G. de Lange (SRON) Laurens Even prof. dr. ir. R.A. Hoekstra (RUG) prof. dr. T. Banerjee (RUG) July 8, 2016 [email protected] student number 2315963 Abstract In this bachelor project research is performed on the design of a prototype low temperature superconducting (LTS) flux pump system. With such a system a superconducting electromagnet can be charged to high currents, while only a low current power supply and cryogenic wiring is necessary. The flux pump could find potential as an application in the SAFARI instrument for the SPICA satellite, but it can also be used for cryogenic energy storage or for offsetting a magnetic field. As a satellite application the flux pump can reduce parasitic heat load on the cold stages of the satellite. Within this thesis we continued the work on an existing flux pump design from a previous bachelor project. This design had previously shown some essential performance characteristics of a flux pump system, but the actual flux pumping was not observed. In this thesis work we investigated the possible causes of this and implemented improvements. These improvements have resulted in a working flux pump system. The main improvement (which was found in a late stage of the project) was the correction of the winding orientation of a secondary coil in the transformer. Other improvements are: (1) the optimization of the transformer cooling, such that higher critical currents in the primary transformer superconducting wire could be achieved, and (2) the increase of the self-inductance of the primary coil of the transformer by replacing the original aluminum transformer core (that will induce eddy currents) by a Vespel polyamide core.
    [Show full text]
  • Flux Pumping Simulation
    HTS Thin Films for Flux Pumping James Gawith Boyang Shen, Jun Ma, Chao Li, Yavuz Ozturk, Tim Coombs University of Cambridge Electrical Power and Energy Conversion Group Contents • Flux pump background • SPICE simulations • HTS thin film AC field switch • Thin film flux pump initial results • Proposed future designs James Gawith Flux Pumps – Superconducting Rectifiers • Wireless (inductive) power supply for superconducting magnets • Provides thermal, mechanical, electrical isolation of magnet • No high-current DC supply or current leads required University of Cambridge/NHMFL University of Cambridge Application: High Field Magnets Application: Compact MRI James Gawith SPICE Simulation • Standard for simulating SMPS • Verified with prototypes • Useful for design and analysis James Gawith Key Findings from Simulation • Superconducting transformer • Power density proportional to operating frequency • Superconducting switches • Operation frequency is limited by on/off switching time • Majority of power loss depends on switch off-state resistance • Maximum pump current limited by switch IC James Gawith AC Field Switch AC Field Switch Developed by Geng [2] ퟒ풂푳풇 푹풅⊥ = 푩풂,⊥ − 푩풕풉,⊥ 푰풄ퟎ (for Ba,⊥ >> Bth,⊥) • Off-state resistance only ≈ 0.2mΩ • Increase frequency and field • Better electromagnets • Use suitable superconductors [2] J. Geng et al., “HTS Persistent Current Switch Controlled by AC Magnetic Field,” IEEE Trans. Appl. Supercond., vol. 26, no. 3, pp. 1–4, Apr. 2016 James Gawith Improved AC Field Switch – Conductor Layer Resistance per meter (Ω) 40μm Copper Stabilizer 0.015 at 77 K 3.8 μm Ag layer at 77 K 0.3 50 μm Hastelloy at 77 K 7.5 Dynamic Resistance of YBCO layer at 100 mT, 1 1.5 kHz Dynamic resistance of ‘2G HTS Wire’.
    [Show full text]
  • Transconductance Quantization in a Topological Josephson Tunnel Junction Circuit
    Transconductance quantization in a topological Josephson tunnel junction circuit L. Peyruchat,1 J. Griesmar,1, 2 J.-D. Pillet,1, 3 and Ç. Ö. Girit1, ∗ 1 Φ0, JEIP, USR 3573 CNRS, Collège de France, PSL University, 11, place Marcelin Berthelot, 75231 Paris Cedex 05, France 2Institut Quantique et Département GEGI, Université de Sherbrooke, Sherbrooke, QC, Canada 3LSI, CEA/DRF/IRAMIS, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France (Dated: September 8, 2020) arXiv:2009.03291v1 [cond-mat.mes-hall] 7 Sep 2020 1 Abstract Superconducting circuits incorporating Josephson tunnel junctions are widely used for funda- mental research as well as for applications in fields such as quantum information and magnetometry. The quantum coherent nature of Josephson junctions makes them especially suitable for metrology applications. Josephson junctions suffice to form two sides of the quantum metrology triangle, relating frequency to either voltage or current, but not its base, which directly links voltage to current. We propose a five Josephson tunnel junction circuit in which simultaneous pumping of 2 flux and charge results in quantized transconductance in units 4e /h = 2e/Φ0, the ratio between the Cooper pair charge and the flux quantum. The Josephson quantized Hall conductance device (JHD) is explained in terms of intertwined Cooper pair pumps driven by the AC Josephson effect. We discuss the experimental implementation as well as optimal configuration of external param- eters and possible sources of error. JHD has a rich topological structure and demonstrates that Josephson tunnel junctions are universal, capable of interrelating frequency, voltage, and current via fundamental constants. Among quantum coherent electronic components the most prominent are Josephson junc- tions and quantum Hall systems.
    [Show full text]
  • C 2016 by Ponnuraj Krishnakumar. All Rights Reserved. CHERN-SIMONS THEORY of MAGNETIZATION PLATEAUS on the KAGOME LATTICE
    c 2016 by Ponnuraj Krishnakumar. All rights reserved. CHERN-SIMONS THEORY OF MAGNETIZATION PLATEAUS ON THE KAGOME LATTICE BY PONNURAJ KRISHNAKUMAR DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics in the Graduate College of the University of Illinois at Urbana-Champaign, 2016 Urbana, Illinois Doctoral Committee: Professor Mike Stone, Chair Professor Eduardo Fradkin, Director of Research Assistant Professor Gregory MacDougall Professor John Stack Abstract Frustrated spin systems on Kagome lattices have long been considered to be a promising candidate for realizing exotic spin liquid phases. Recently, there has been a lot of renewed interest in these systems with the discovery of experimental materials such as Volborthite and Herbertsmithite that have Kagome like structures. In this thesis I will focus on studying frustrated spin systems on the Kagome lattice using a spin-1/2 antiferromagnetic XXZ Heisenberg model in the presence of an external magnetic field as well as other perturbations. Such a system is expected to give rise to magnetization platueaus which can exhibit topological characteristics in certain regimes. We will first develop a flux-attachment transformation that maps the Heisenberg spins (hard-core bosons) onto a problem of fermions coupled to a Chern-Simons gauge field. This mapping relies on being able to define a consistent Chern-Simons term on the lattice. Using this newly developed mapping we analyse the phases/magnetization plateaus that arise at the mean-field level and also consider the effects of adding fluctuations to various mean-field states. Along the way, we show how to discretize an abelian Chern-Simons gauge theory on generic 2D planar lattices that satisfy certain conditions.
    [Show full text]
  • An Overview of Flux Pumps for HTS Coils T
    ID: ASC2016-5LOr1A-04A 1 An Overview of Flux Pumps for HTS Coils T. A. Coombs, Senior Member, IEEE, J. Geng, L. Fu, and K. Matsuda field varying with time and in space, in which the waveform is Abstract—High-Tc Superconducting (HTS) flux pumps are moving relative to the superconductor and which do not rely on capable of injecting flux into closed HTS magnets without switches or a normal spot. This was important because all electrical contact. It is becoming a promising alternative of current preceding methods required either a moving normal spot or source in powering HTS coils. This paper reviews the recent superconducting switches and this has restricted their use. Thus progress in flux pumps for HTS coil magnets. Different types of for example in [12][13][14], Chung proposed a linear electro- HTS flux pumps are introduced. The physics of these flux pumps are explained and comparisons are made. magnet flux pump for HTS magnets, yet this relied on inducing a moving normal spot in a Niobium sheet. Nakamura [15] proposed a similar arrangement but pointed out that MgB2 Index Terms—Coated conductor coils, flux pump, HTS. could be used rather than Niobium but their method still required a normal spot. Similarly Bai [16][17][18] achieved flux pumping using a BSCCO sheet and MgB2 sheet but in [17] I. INTRODUCTION they attribute the operation to the motion of a normal spot. HANKS to the progress in manufacturing long length T Coated Conductors (CC), CC coils are becoming more and A travelling wave and the equivalent circuit for its operation are more popular for magnets.
    [Show full text]
  • A Kilo-Ampere Level HTS Flux Pump
    A kilo-Ampere level HTS flux pump Jianzhao Geng1, a), Tom Painter 2), Peter Long 1), Jamie Gawith 1), Jiabin Yang 1), Jun Ma 1), Qihuan Dong1), Boyang Shen1), Chao Li 1), and T. A. Coombs 1,a) 1) Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, United Kingdom 2) National High Magnetic Field Lab, Tallahassee, FL 32310, USA a) Email: [email protected], [email protected] Abstract This paper reports a newly developed high current transformer-rectifier High-Tc Superconducting (HTS) flux pump switched by dynamic resistance. A quasi-persistent current of over 1.1 kA has been achieved at 77 K using the device, which is the highest reported operating current by any HTS flux pumps to date. The size of the device is much smaller than traditional current leads and power supplies at the same current level. Parallel YBCO coated conductors are used in the transformer secondary winding as well as in the superconducting load coil to achieve high current. The output current is limited by the critical current of the load rather than the flux pump itself. Moreover, at over 1 kA current level, the device can maintain high flux injection accuracy, and the overall flux ripple is less than 0.2 mili-Weber. The work has shown the potential of using the device to operate high field HTS magnets in ultra-high quasi-persistent current mode, thus substantially reducing the inductance, size, weight, and cost of high field magnets, making them more accessible. It also indicates that the device is promising for powering HTS NMR/MRI magnets, in which the requirement for magnetic field satiability is demanding.
    [Show full text]
  • MINIATURE PENNING CELL ARRAY for ON-CHIP VACUUM PUMPING Scott R
    MINIATURE PENNING CELL ARRAY FOR ON-CHIP VACUUM PUMPING Scott R. Green and Yogesh B. Gianchandani University of Michigan Engineering Research Center for Wireless Integrated Microsystems (WIMS), Ann Arbor, Michigan, USA ABSTRACT This paper presents a miniaturized Penning cell array for on-chip sputter-ion vacuum pumping. The effects of miniaturization on pumping performance – including cut-off magnetic flux, pumping rate, and minimum operating pressure – are examined. The pump is experimentally shown to reduce pressure by 600 mTorr (80 Pa) from a starting pressure of 18 Torr (2.4 kPa) in 30 minutes of operation. The rate of molecular removal is typically 3-15 x 1013 molecules per second. The architecture allows device operation at pressures at least as low as 70 mTorr (9.3 Pa), representing an improvement of two orders of magnitude over previously reported micro-sputter-ion pumps. INTRODUCTION Figure 1: MEMS devices requiring precise high-vacuum On-chip vacuum generation is an attractive alternative pressure levels for operation can be packaged with a and complement to vacuum sealing for microsystems that Penning cell array sputter-ion pump. require very long-term or very precise control over package work presents theoretical modeling and experimental pressure, including chip-scale atomic clocks and micro- validation of a miniature Penning cell array SIP architecture. mass spectrometers. In micro-scale packages with reduced volumes, the pressure increase due to even small outgassing DESIGN AND MODELING and leakage sources is amplified. Thus, the presence of a A single Penning cell consists of a cylindrical anode pump can add to system robustness and decreased sandwiched between two planar titanium cathodes, resulting requirements for hermetic sealing and use of low outgassing in radially-directed electric field lines at the mid-length of materials.
    [Show full text]
  • Ba-Cu-O Bulk High-Temperature Superconductors
    IEEE/CSC & ESAS EUROPEAN SUPERCONDUCTIVITY NEWS FORUM, No. 19, January 2012 Materials Process and Applications of Single Grain (RE)-Ba-Cu-O Bulk High-temperature Superconductors Beizhan Li, Difan Zhou, Kun Xu, Shogo Hara, Keita Tsuzuki, Motohiro Miki, Brice Felder, Zigang Deng and Mitsuru Izumi* Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology (TUMSAT), 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533, Japan *E-mail: [email protected] Abstract - This paper reviews recent advances in the melt process of (RE)-Ba-Cu-O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTS), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices. Preprint of plenary SCC paper submitted to Physica C (should be cited accordingly) Submitted to ESNF November 30, 2011; accepted Dec. 6, 2011. Reference No. CR24; Category 3. Keywords – rare earth, cuprate, high-temperature superconductor, HTS, bulk superconductor, melt growth process, flux pinning, MAGLEV, MRI, Flywheel, Motor I.
    [Show full text]
  • 3D Modeling of a Superconducting Dynamo-Type Flux Pump
    www.nature.com/scientificreports OPEN 3D modeling of a superconducting dynamo‑type fux pump Asef Ghabeli1, Enric Pardo1* & Milan Kapolka1,2 High temperature superconducting (HTS) dynamos are promising devices that can inject large DC currents into the winding of superconducting machines or magnets in a contactless way. Thanks to this, troublesome brushes in HTS machines or bulky currents leads with high thermal losses will be no longer required. The working mechanism of HTS dynamo has been controversial during the recent years and several explanations and models have been proposed to elucidate its performance. In this paper, we present the frst three‑dimensional (3D) model of an HTS fux pump, which has good agreement with experiments. This model can be benefcial to clarify the mechanism of the dynamo and pinpoint its unnoticed characteristics. Employing this model, we delved into the screening current and electric feld distribution across the tape surface in several crucial time steps. This is important, since the overcritical screening current has been shown to be the reason for fux pumping. In addition, we analyzed the impact of both components of electric feld and screening current on voltage generation, which was not possible in previous 2D models. We also explored the necessary distance of voltage taps at diferent airgaps for precise measurement of the voltage across the tape in the dynamo. Since 1960s, when the frst generation of superconducting fux pumps have been designed and operated, the fux pump technology has undergone a remarkable developement1–5. Within around 60 years, various mechanically or electrically driven superconducting fux pumps have been operated using low-temperature superconductor (LTS) materials in their previous generation and high-temperature superconductor (HTS) materials in their last generation.
    [Show full text]
  • Origin of DC Voltage in Type II Superconducting Flux Pumps: Field, Field Rate of Change, and Current Density Dependence of Resistivity J
    Origin of DC voltage in type II superconducting flux pumps: field, field rate of change, and current density dependence of resistivity J. Geng,1 K. Matsuda,1,2 L. Fu,1 J-F Fagnard,3 H. Zhang,1 X. Zhang,1 B. Shen,1 Q. Dong,1 M. Baghdadi,1 and T. A. Coombs1 1 Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, United Kingdom 2 Magnifye Ltd., Cambridge, CB5 8DD United Kingdom 3. Montefiore Institute, Liège University, B-4000 Liège, Belgium Email: [email protected] Superconducting flux pumps are the kind of devices which can generate direct current into superconducting circuit using external magnetic field. The key point is how to induce a DC voltage across the superconducting load by AC fields. Giaever [1] pointed out flux motion in superconductors will induce a DC voltage, and demonstrated a rectifier model which depended on breaking superconductivity. Klundert et al. [2, 3] in their review(s) described various configurations for flux pumps all of which relied on inducing the normal state in at least part of the superconductor. In this letter, following their work, we reveal that a variation in the resistivity of type II superconductors is sufficient to induce a DC voltage in flux pumps and it is not necessary to break superconductivity. This variation in resistivity is due to the fact that flux flow is influenced by current density, field intensity, and field rate of change. We propose a general circuit analogy for travelling wave flux pumps, and provide a mathematical analysis to explain the DC voltage.
    [Show full text]
  • Transconductance Quantization in a Topological Josephson Tunnel Junction Circuit
    PHYSICAL REVIEW RESEARCH 3, 013289 (2021) Transconductance quantization in a topological Josephson tunnel junction circuit L. Peyruchat,1 J. Griesmar ,1,* J.-D. Pillet ,1,2 and Ç. Ö. Girit 1,† 1 Flux Quantum Lab (0), JEIP, USR 3573 CNRS, Collège de France, PSL University, 11, place Marcelin Berthelot, 75231 Paris Cedex 05, France 2LSI, CEA/DRF/IRAMIS, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France (Received 25 September 2020; revised 1 February 2021; accepted 2 February 2021; published 29 March 2021) Superconducting circuits incorporating Josephson tunnel junctions are widely used for fundamental research as well as for applications in fields such as quantum information and magnetometry. The quantum coherent nature of Josephson junctions makes them especially suitable for metrology applications. Josephson junctions suffice to form two sides of the quantum metrology triangle, relating frequency to either voltage or current, but not its base, which directly links voltage to current. We propose a five Josephson tunnel junction circuit in which 2 simultaneous pumping of flux and charge results in quantized transconductance in units 4e /h = 2e/0,the ratio between the Cooper pair charge and the flux quantum. The Josephson quantized Hall conductance device (JHD) is explained in terms of intertwined Cooper pair pumps driven by the AC Josephson effect. We describe an experimental implementation of the device and discuss the optimal configuration of external parameters and possible sources of error. The JHD has a rich topological structure and demonstrates that Josephson tunnel junctions are universal, capable of interrelating frequency, voltage, and current via fundamental constants. DOI: 10.1103/PhysRevResearch.3.013289 I.
    [Show full text]
  • PERFORMANCE ANALYSIS of LOW TEMPERATURE SUPERCONDUCTING FLUX PUMP Researched at SRON Groningen, the Netherlands
    Bachelors Thesis in Applied Physics PERFORMANCE ANALYSIS OF LOW TEMPERATURE SUPERCONDUCTING FLUX PUMP Researched at SRON Groningen, the Netherlands July, 2017 James Robert Lyon, S2709821 [email protected] / (+31)619671537 Faculty of Science and Engineering University of Groningen Supervised by dr. ir. G. de Lange (SRON) prof. dr. ir. C.H. van der Wal (RUG) prof. dr. T. Banerjee (RUG) 1 [This page intentionally left blank] 2 Abstract A flux pump system uses a small alternating current to build up a large current inside a superconducting load coil. An experimental prototype has been built for the purpose of analysing its performance, including its stability, reliability and limiting, for possible satellite application at SRON. The flux pump circuit is a developing project previously worked upon by two other Bachelor students. The operation of the full wave transformer rectifier flux pump is described and analysed. The experimental set-up was rebuilt, measurement methods were developed and sensors were calibrated. The optimal primary wave for this device was experimentally determined to have a frequency of 0.1667 Hz and amplitude of 250 mA from which an exponential increase was observed and a maximum output of approximately 7 A was achieved. However, it proved to be an unreliable system as repeated experiments provided inconsistent results due to suspected short circuiting of inductors. Moreover, the power and efficiency of the system is analysed and is in good agreement with theoretical predications. The flux pump has a maximum efficiency of 80% at a normalised current of 0.2. 3 Contents Abstract ................................................................................................................................................................................. 3 Acknowledgments ...............................................................................................................................................................
    [Show full text]