Expansion of a superconducting vortex core into a diffusive metal

Stolyarov, V. S.; Cren, Tristan; Brun, Christophe; Golovchanskiy, I. A.; Skryabina, O. V.; Kasatonov, Daniil; Khapaev, M. M.; Kupriyanov, M. Yu.; Golubov, A. A.; Roditchev, Dimitri

doi:10.1038/s41467-018-04582-1

Cited by 35 publications

(41 citation statements)

References 57 publications

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“…The particular case of a bilayer structure, combining a normal and superconducting thin film, results in the existence of superconducting correlations in the metal, characterized by the formation of a minigap, while the superconducting order parameter inside the superconducting material will be partially suppressed [5][6][7]. In addition, the coherence length will drastically expand inside the diffusive metal [8]. This resulting expansion of the vortex core will have an important impact on the observed vortex distributions because (i) the interaction between vortices will be nonuniform throughout the bilayer and (ii) the interaction of the vortex distribution with a nanostructured environment is dependent on the ratio between the characteristic length scale of the condensate, i.e., the coherence length, and the actual size of the nanostructure [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Exploring the impact of core expansion on the vortex distribution in superconducting–normal-metal hybrid nanostructures

et al. 2019

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The superconducting condensate in a bilayer normal-metal-superconducting film has a nonuniform dependence throughout the layer. For sufficiently thin normal metallic films, the superconducting correlations induced by the contacting superconducting layer result in the formation of a minigap and the characteristic length scales governing the response of the condensate will be different. In this work we use scanning tunneling spectroscopy to visualize the vortex states as a function of the applied magnetic field in a Au-MoGe nanostructure. By comparing the obtained zero-bias conductance maps with time-dependent Ginzburg-Landau simulations, we directly confirm that the observed vortex distributions can only be explained by taking into account the impact of the normal metallic layer. We illustrate this impact on the vortex state for two lithographically fabricated mesoscopic bilayer structures containing an identical antidot array but having different lateral sizes.

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Section: Introductionmentioning

confidence: 99%

Exploring the impact of core expansion on the vortex distribution in superconducting–normal-metal hybrid nanostructures

et al. 2019

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“…Finally, we Taylor expand eA = −nπ/r + O(1/r 2 ) and keep only the first term. Equation (11) can now be solved exactly, and by applying the linearized boundary conditions the solution can be written on the form…”

Section: Resultsmentioning

confidence: 99%

“…Thus, these vortex loops are easily tunable. This makes it possible to make the vortices touch the surface, leaving distinct traces which are directly observable by scanning tunneling spectroscopy [11].Vortex loops in superconducting systems has previously been predicted using the phenomenological Ginzburg-Landau theory [6][7][8]. Here we use a fully microscopic framework known as quasiclassical theory and solve the Usadel equation relevant for diffusive systems [12].…”

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confidence: 99%

Controllable vortex loops in superconducting proximity systems

Fyhn

Linder

2019

Phys. Rev. B

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Superconducting vortex loops have so far avoided experimental detection despite being the focus of much theoretical work. We here propose a method of creating controllable vortex loops in the superconducting condensate arising in a normal metal through the proximity effect. We demonstrate both analytically and numerically that superconducting vortex loops emerge when the junction is pierced by a current-carrying insulated wire and give an analytical expression for their radii. The vortex loops can readily be tuned big enough to hit the sample surface, making them directly observable through scanning tunneling microscopy. Introduction:Many key properties of physical systems are determined by topological defects such as dislocations in solids, domain walls in ferroics, vortices in superfluids, magnetic skyrmions in condensed matter systems and cosmic strings in quantum field theories. In superconductors, the topological entities are vortex lines of quantized magnetic flux. The topological nature of these vortices makes them stable, which is important for potential applications such as superconducting qubits [1-3], digital memory and long-range spin transport [4]. Vortices have non-superconducting cores and a phase winding of an integer multiple of 2π in the superconducting order parameter, leading to circulating supercurrents [5].The formation of superconducting vortex loops is topologically allowed, and has theoretically been predicted to form around strong magnetic inclusions inside the superconductor [6] or through vortex cutting and recombination [7,8]. However, no observation of vortex loops in superconducting systems has been found to date. One challenging aspect is that vortex loops are typically small in conventional superconductors and difficult to stabilize for an extended period of time [9]. Recently it has been shown that vortex loops can be formed in proximity systems by inserting physical barriers, around which the vortices can wrap [8].In this Letter, we present a way to create controllable vortices in mesoscopic proximity systems in a manner which makes them experimentally detectable through scanning tunneling microscopy. The system considered is a three-dimensional SNS junction pierced by a current-carrying wire which creates the inhomogeneous field responsible for the vortex loops. In planar SNS-junctions with uniform applied magnetic field, changing the superconducting phase difference between the two superconductors shifts the vortex lines in the vertical direction [10]. We here show that the corresponding effect on vortex loops in three dimensions is to change their size. Thus, these vortex loops are easily tunable. This makes it possible to make the vortices touch the surface, leaving distinct traces which are directly observable by scanning tunneling spectroscopy [11].Vortex loops in superconducting systems has previously been predicted using the phenomenological Ginzburg-Landau theory [6][7][8]. Here we use a fully microscopic framework known as quasiclassical theory and solve the Usadel equ...

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“…It is known that vortices can form also inside normal metals that are in the proximity to a superconductor [20][21][22][23]. Cooper pairs can then leak into the normal metal through the process FIG.…”

Section: Introductionmentioning

confidence: 99%

Superconducting vortices in half-metals

Fyhn

Linder

2019

Phys. Rev. B

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When the impurity mean free path is short, only spin-polarized Cooper pairs which are non-locally and antisymmetrically correlated in time may exist in a half-metallic ferromagnet. As a consequence, the half-metal acts as an odd-frequency superconducting condensate. We demonstrate both analytically and numerically that quantum vortices can emerge in half-metals despite the complete absence of conventional superconducting correlations. Because these metals are conducting in only one spin band, we show that a circulating spin supercurrent accompanies these vortices. Moreover, we demonstrate that magnetic disorder at the interfaces with the superconductor influences the position at which the vortices nucleate. This insight can be used to help determine the effective interfacial misalignment angles for the magnetization in hybrid structures, since the vortex position is experimentally observable via STM-measurements. We also give a brief discussion regarding which superconducting order parameter to use for odd-frequency triplet Cooper pairs in the quasiclassical theory. arXiv:1904.04846v4 [cond-mat.supr-con] 5 Jan 2020

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Expansion of a superconducting vortex core into a diffusive metal

Cited by 35 publications

References 57 publications

Exploring the impact of core expansion on the vortex distribution in superconducting–normal-metal hybrid nanostructures

Exploring the impact of core expansion on the vortex distribution in superconducting–normal-metal hybrid nanostructures

Controllable vortex loops in superconducting proximity systems

Superconducting vortices in half-metals

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