Direct Observation of Vortex Shells and Magic Numbers in Mesoscopic Superconducting Disks

Grigorieva, I. V.; Escoffier, Walter; Richardson, J.; Vinnikov, L. Ya.; Dubonos, S. V.; Oboznov, V. A.

doi:10.1103/physrevlett.96.077005

Cited by 123 publications

(161 citation statements)

References 27 publications

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“…5, we observed a one dimensional vortex distribution on an annulus, and found that the vortex spacing (a) did not follow the Abrikosov lattice derived from the GL equation, 2 √3 ⁄ / for a close-packed hexagonal array; this equation leads to sparse vortices at low fields (H < 0.7 T) and dense vortices at high fields (H > 0.7 T). In previous measurements of mesoscopic superconducting disks [4,16,45], the first vortex is typically observed in the center of the disk in contrast to the results in Fig. 5.…”

Section: Islandscontrasting

confidence: 53%

“…When the size of a superconductor becomes comparable with these characteristic lengths, the properties of the superconductor can change dramatically, including the critical temperature, critical magnetic field, and vortex structures. Early work focused on the effect of condensate confinement in mesoscopic disks [2][3][4], and the effect of symmetry [5] in comparing disks, squares [6], and mesoscopic triangles [7]. Focus on vortex states in mesoscopic superconductors, both theoretical and experimental, revealed multi-vortex Abrikosov-like states with spatial arrangements of singly quantized vortices, or giant vortex states depending on details of the condensate confinement [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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Creating nanostructured superconductors on demand by local current annealing

Baek

Zhang

et al. 2015

Phys. Rev. B

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Abstract:Superconductivity results from a Bose condensate of Cooper-paired electrons with a macroscopic quantum wavefunction. Dramatic effects can occur when the region of the condensate is shaped and confined to the nanometer scale. Recent progress in nanostructured superconductors has revealed a route to topological superconductivity, with possible applications in quantum computing. However, challenges remain in controlling the shape and size of specific superconducting materials. Here, we report a new method to create nanostructured superconductors by partial crystallization of the half-Heusler material, YPtBi. Superconducting islands, with diameters in the range of 100 nm, were reproducibly created by local current annealing of disordered YPtBi in the tunneling junction of a scanning tunneling microscope (STM). We characterize the superconducting island properties by scanning tunneling spectroscopic measurements to determine the gap energy, critical temperature and field, coherence length, and vortex formations. These results show unique properties of a confined superconductor and demonstrate that this new method holds promise to create tailored superconductors for a wide variety of nanometer scale applications.

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Section: Islandscontrasting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Creating nanostructured superconductors on demand by local current annealing

Baek

Zhang

et al. 2015

Phys. Rev. B

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“…Skyrmions have many features in common with Abrikosov vortices in superconductors (28,29). They are both condensed into a triangular lattice in bulk or 2D films due to the minimization of their repulsive interactions.…”

Section: Discussionmentioning

confidence: 99%

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Zhao

Jin

Wang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

138

114

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Magnetic skyrmion is a nanosized magnetic whirl with nontrivial topology, which is highly relevant for applications on future memory devices. To enable the applications, theoretical efforts have been made to understand the dynamics of individual skyrmions in magnetic nanostructures. However, directly imaging the evolution of highly geometrically confined individual skyrmions is challenging. Here, we report the magnetic field-driven dynamics of individual skyrmions in FeGe nanodisks with diameters on the order of several skyrmion sizes by using Lorentz transmission electron microscopy. In contrast to the conventional skyrmion lattice in bulk, a series of skyrmion cluster states with different geometrical configurations and the fielddriven cascading phase transitions are identified at temperatures far below the magnetic transition temperature. Furthermore, a dynamics, namely the intermittent jumps between the neighboring skyrmion cluster states, is found at elevated temperatures, at which the thermal energy competes with the energy barrier between the skyrmion cluster states.T he complex spin configurations in helimagnets have attracted considerable attention recently, with the topologically stable particle-like spin texture with a size down to the nanoscale, namely magnetic skyrmion, as the focus of interest (1). Magnetic skyrmion is characterized as a nanoscale topological particle producing unconventional spin electronic phenomena (2, 3) that holds great promise for future spintronic devices, including racetrack memory (4), magnetic random access memory, and magnetic sensors (1). Essentially, such schemes rely on the controllable formation and manipulation of individual skyrmions at nanostructured elements with various shapes such as disks, stripes, or wires (5-7). Investigation of skyrmions in confined geometries has therefore become one of the major topics in the field of skyrmion physics (5-10).Unlike ordinary magnetic vortices in microsized soft magnetic disks due to the minimization of the dipolar energy (11), the key ingredient of stabilizing skyrmions in helimagnets is the antisymmetry Dzyaloshinskii−Moriya (DM) interactions originating from the broken inversion symmetry (12). The competition of the DM coupling with ferromagnetic exchange interaction results in periodic helical ground state in helimagnets. Under the action of a magnetic field and temperature, these magnetic helices transfer into skyrmion crystal with triangular lattice configuration, and finally to the field-polarized ferromagnetic state. Notably, both ferromagnetic and DM couplings occur among the neighboring spins and belong to short-range interaction. Thus, it was demonstrated theoretically that skyrmions cluster states, characterized by certain arrangements of limited skyrmions, still persist even in submicrometer objects (8, 13). There, the longrange lattice form of skyrmions in 2D or bulk helimagnets is broken, but a short-ranged ordering with specific geometrical symmetries still remains, and the number of skyrmions in the cluster...

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“…Very recently, Grigorieva et al 22 succeeded in the direct observation of vortex shells in mesoscopic superconducting Nb disks using the Bitter decoration technique. At fixed temperature, they studied well-defined shell structures containing up to 40 vortices and identified rules of shell filling and magic numbers, in agreement with Ref.…”

Section: Introductionmentioning

confidence: 99%

Multivortex and giant vortex states near the expulsion and penetration fields in thin mesoscopic superconducting squares

et al. 2006

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The temperature dependence of the vortex penetration and expulsion magnetic fields are investigated, both theoretically and experimentally, for mesoscopic superconducting squares. The small-tunnel-junction method is used to determine the transition fields between the different vortex states. We found that the penetration fields decrease with increasing temperature, while the expulsion fields for a particular vorticity may increase, decrease or be independent of temperature. Using the Ginzburg-Landau theory we link the different temperature dependencies to the configuration of the vortex state, i.e. giant vortex state versus multivortex state. The vortex state consisting of four vortices has a larger stability region which is most pronounced in a certain hightemperature range.

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Direct Observation of Vortex Shells and Magic Numbers in Mesoscopic Superconducting Disks

Cited by 123 publications

References 27 publications

Creating nanostructured superconductors on demand by local current annealing

Creating nanostructured superconductors on demand by local current annealing

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Multivortex and giant vortex states near the expulsion and penetration fields in thin mesoscopic superconducting squares

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