Magnetic flux structures of finite superconducting networks

Kato, Masaru; Sato, Osamu

doi:10.1088/0953-2048/26/3/033001

Cited by 9 publications

(11 citation statements)

References 100 publications

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“…This matching effect has been ascribed to enhancement of the vortex lattice pinning by the artificial lattice at matching conditions, i. e. when there are integer number of vortices per plaquette [7]. Similar magnetoresistance minima and ordered magnetic flux structures [9,10] can be induced, assuming a very different scenario: Little-Parks critical temperature oscillations in a wire network. Recently, Zhang et al [11] have reported that interstitial vortex state and wire network-like state could be reached increasing the applied magnetic field, at constant temperature, in Nb films with array of large antidots (holes).…”

Section: Introductionmentioning

confidence: 99%

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Gómez¹,

Valle²,

González³

et al. 2014

Supercond. Sci. Technol.

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Abstract. Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current I c (H), magnetization M(H) and ac-susceptibility  ac (H) in a broad temperature range. Due to the coherence length divergence at T c , a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to T c , wire network behaviour is only present in a very narrow temperature window close to T c . In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.

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Section: Introductionmentioning

confidence: 99%

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Gómez¹,

Valle²,

González³

et al. 2014

Supercond. Sci. Technol.

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“…The current induced switching of a superconducting nano-ring with two arms into a SQUID can be understood considering the non-uniform order parameter along the ring in such a structure when a magnetic field is applied1920212223. Based on the Ginzburg-Landau equations, de-Gennes19 and Alexander20 showed that two minima of the order parameter are generated at equal distances from the connection points of the arms to the ring2021.…”

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confidence: 99%

Current-induced SQUID behavior of superconducting Nb nano-rings

Sharon

Shaulov

Berger

et al. 2016

Sci Rep

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The critical temperature in a superconducting ring changes periodically with the magnetic flux threading it, giving rise to the well-known Little-Parks magnetoresistance oscillations. Periodic changes of the critical current in a superconducting quantum interference device (SQUID), consisting of two Josephson junctions in a ring, lead to a different type of magnetoresistance oscillations utilized in detecting extremely small changes in magnetic fields. Here we demonstrate current-induced switching between Little-Parks and SQUID magnetoresistance oscillations in a superconducting nano-ring without Josephson junctions. Our measurements in Nb nano-rings show that as the bias current increases, the parabolic Little-Parks magnetoresistance oscillations become sinusoidal and eventually transform into oscillations typical of a SQUID. We associate this phenomenon with the flux-induced non-uniformity of the order parameter along a superconducting nano-ring, arising from the superconducting leads (‘arms’) attached to it. Current enhanced phase slip rates at the points with minimal order parameter create effective Josephson junctions in the ring, switching it into a SQUID.

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“…At the contacts between the ring and the connectors, we require continuity of the potential and of the order parameter. Charge conservation requires that the sum of total currents along the branches of the loop has to equal the current along the connectors, but assuming that decay or formation of Cooper pairs requires a finite volume, and following [33,34], we impose the stronger constraint 3 n=1 ±Dψ n = 0, where n stands for each wire that meets at the contact, we have taken the case that the three wires have the same cross section at the contact, and the sign depends on whether the current is entering or leaving the contact.…”

Section: Basic Modelmentioning

confidence: 99%

The Stationary SQUID

Berger

2018

J Low Temp Phys

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In the customary mode of operation of a SQUID, the electromagnetic field in the SQUID is an oscillatory function of time. In this situation, electromagnetic radiation is emitted, and couples to the sample. This is a back-action that can alter the state that we intend to measure. A circuit that could perform as a stationary SQUID consists of a loop of superconducting material that encloses the magnetic flux, connected to a superconducting and to a normal electrode. This circuit does not contain Josephson junctions, or any other miniature feature. We study the evolution of the order parameter and of the electrochemical potential in this circuit; they converge to a stationary regime and the voltage between the electrodes depends on the enclosed flux. We obtain expressions for the power dissipation and for the heat transported by the electric current; the validity of these expressions does not rely on a particular evolution model for the order parameter. We evaluate the influence of fluctuations. For a SQUID perimeter of the order of 1µm and temperature 0.9T c , we obtain a flux resolution of the order of 10 −5 Φ 0 /Hz 1/2 ; the resolution is expected to improve as the temperature is lowered.

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Magnetic flux structures of finite superconducting networks

Cited by 9 publications

References 100 publications

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Current-induced SQUID behavior of superconducting Nb nano-rings

The Stationary SQUID

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