Matching fields of a long superconducting film

Sardella, Edson; Doria, Mauro M.; Netto, Paulo R. S.

doi:10.1103/physrevb.60.13158

Cited by 24 publications

(25 citation statements)

References 9 publications

(19 reference statements)

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“…11 Interestingly, further increasing the field, first an almost square array of vortices is observed 12 before a more disordered configuration is achieved. The field H p at which the first vortex penetrates in narrow stripes and the formation of different vortex patterns have been previously investigated both theoretically [12][13][14][15][16][17][18][19][20] and experimentally. [21][22][23][24][25][26][27][28] Similarly to early scanning Hall experiments performed by Stan et al 27 in Nb stripes, our determination of H p is about four times larger than the one predicted theoretically.…”

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Direct visualization of the Campbell regime in superconducting stripes

et al. 2010

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A combination of scanning Hall microscopy and scanning ac-susceptibility measurements in superconducting stripes ͑ribbons͒ of width w Ͻ 10 m was used to observe the dimensional phase transitions of the vortex lattice and its stability under alternating fields. At low dc magnetic fields applied perpendicularly to the plane of the stripes, vortices form a one-dimensional chain at the center of the stripes. Above a certain field H ‫ء‬ ͑w͒, the vortex chain splits in two parallel rows displaced laterally in such a way that a zigzag vortex pattern is observed. By shaking the vortices with an external magnetic ac field and detecting their in-phase motion locally, we can identify the degree of mobility of each individual vortex. This technique allows us ͑i͒ to directly visualize the transition from intravalley ͑Campbell regime͒ to intervalley vortex motion as the amplitude of the ac modulation is increased and ͑ii͒ to accurately determine the temperature at which the vortex lattice freezes in a field-cooling experiment. The hallmark of type II superconductivity is the presence of quantized magnetic flux encircled by a rotating condensate of paired electrons when a sufficiently strong magnetic field is applied. The free motion of these fluxons leads to dissipation thus destroying the perfect conductivity of the system. The ever growing electricity demand has motivated for several decades a fierce strive for understanding, improving, and optimizing the mechanisms to prevent the fluxon's motion by introducing a rich diversity of pinning centers. 1Among the most powerful experimental methods used to determine the efficiency of pinning sites is the ac-susceptibility technique which consist of shaking the flux-line lattice with a small alternating magnetic field while recording its in-phase magnetic response.2 Pioneering theoretical works by Campbell and co-workers substantially contributed to comprehend and interpret the ac response of a superconducting system. 3,4 In the most simple version, two different regimes with distinctive ac responses can be identified. For a gentle ac shacking, flux lines oscillate inside the pinning potential following a reversible and low dissipative motion ͑Campbell regime͒. By increasing the strength of the ac excitation, the intravalley vortex motion first senses the anharmonicities of the potential well and eventually switches to an intervalley motion where vortices can hop from one pinning site to another. 5So far, all the experimental and theoretical reports are focused on global ac-susceptibility investigations where the recorded signal represents an average over millions of flux lines each of which trapped in a different pinning potential and subjected to a different environment. [6][7][8] In this paper, we introduce a local vortex imaging technique with singlevortex resolution which allows us to directly visualize the oscillatory motion of individual vortices submitted to harmonic ac excitations. The system to investigate consists of superconducting ribbons which, due to the proximity o...

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Direct visualization of the Campbell regime in superconducting stripes

et al. 2010

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“…39,40 , for example. In this paper we will study multivortex states where many vortices nucleate, yielding a triangular lattice in the center of the disk and a ringlike structure close to the edges.…”

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From vortex molecules to the Abrikosov lattice in thin mesoscopic superconducting disks

2004

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Stable vortex states are studied in large superconducting thin disks (for numerical purposes we considered with radius R = 50ξ). Configurations containing more than 700 vortices were obtained using two different approaches: the nonlinear Ginzburg-Landau (GL) theory and the London approximation. To obtain better agreement with results from the GL theory we generalized the London theory by including the spatial variation of the order parameter following Clem's ansatz. We find that configurations calculated in the London limit are also stable within the Ginzburg-Landau theory for up to ∼ 230 vortices. For large values of the vorticity (typically, L 100), the vortices are arranged in an Abrikosov lattice in the center of the disk, which is surrounded by at least two circular shells of vortices. A Voronoi construction is used to identify the defects present in the ground state vortex configurations. Such defects cluster near the edge of the disk, but for large L also grain boundaries are found which extend up to the center of the disk.

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“…For example, for Yukawa particles the direct 2 − 3-transition was observed in dusty plasma clusters 24 with increasing linear density. In addition, a SOT has been predicted theoretically for an Abrikosovvortex arrangement in a superconducting slab for low temperatures [25][26][27][28][29] , for Pearl vortices 30 , and also for binary mixtures of repulsive particles 31 , in particular, when the ratio between charges of both species was around 1/5.…”

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Generic ordering of structural transitions in quasi-one-dimensional Wigner crystals

Galván-Moya

Peeters

2014

Phys. Rev. B

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We investigate the dependence of the structural phase transitions in an infinite quasi-onedimensional system of repulsively interacting particles on the profile of the confining channel. Three different functional expressions for the confinement potential related to real experimental systems are used that can be tuned continuously from a parabolic to a hard-wall potential in order to find a thorough understanding of the ordering of the chain-like structure transitions. We resolve the longstanding issue why the most theories predicted a 1-2-4-3-4 sequence of chain configurations with increasing density, while some experiments found the 1-2-3-4 sequence.

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Matching fields of a long superconducting film

Cited by 24 publications

References 9 publications

Direct visualization of the Campbell regime in superconducting stripes

Direct visualization of the Campbell regime in superconducting stripes

From vortex molecules to the Abrikosov lattice in thin mesoscopic superconducting disks

Generic ordering of structural transitions in quasi-one-dimensional Wigner crystals

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