Shape induced anomalies in vortex pinning and dynamics of superconducting antidot arrays with spherical cavities

Abstract

Using electrochemical deposition of Pb in the pores of templates prepared by self-assembly from colloidal suspensions of polystyrene latex spheres, well ordered superconducting antidot arrays with spherically shaped holes are fabricated. In contrast to conventional lithographic arrays the samples with spherical cavities demonstrate significantly reduced pinning strength favoring the formation of commensurate states. The ac-flux penetration acquires a hybrid intra-and intervalley regime. For high ac drives an unusual inversion to paramagnetic ac shielding is found at commensurate states.

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

“…The solid thick lines were obtained using the full equation (16), with n = 2, while dashes represent the large α p approximation [Eq. (21)]. The transition between the high-temperature, highly mobile regime, with a large ac penetration depth, to the lowtemperature frozen state, where Λ ac ≈ Λ, is very clear.…”

“…Additional depletion can also be attributed to the long range nature of the screening current. 47,48 However, the experimental observation in antidot systems of pronounced matching effects at values of the applied field that coincide with the expected flux-density, µ 0 H = nB 1 , [10][11][12][13][14][15][16][17][18][19][20][21][22] suggests that the depletion zone is much narrower than the sample itself. In any case, as shown in the Supplemental Material, our results do not depend strongly on the width of the fluxdepleted region.…”

“…[10][11][12] This reflects in different (according to whether or not interstitial vortices are present) scenarios of the sample response to an excitation, as indeed observed in a great deal of macroscopic ac-susceptibility experiments. [13][14][15][16][17][18][19][20][21][22] The interpretation of the different dynamical regimes usually ig-nores the random pinning potential produced by sample inhomogeneities, considered negligible at the temperatures where the experiments are carried out. However, at least for experiments performed within the linear regime, where vortices are driven close to their equilibrium positions by very small driving forces, the weak material pinning might become important or even dominant.…”

Superconducting properties of a parallelepiped mesoscopic superconductor: A comparative study between the 2D and 3D Ginzburg–Landau models

“…They are two coupled partial differential equations, one for the order parameter ψ and another one for the vector potential A which is related to the local magnetic field through the expression h = ∇ × A. We have: (2), A x and J sx ( X ), A y and J sy (Y ),…”

“…In particular, as a consequence of the demagnetization effects, when the size of the sample along the direction of the applied magnetic field is smaller than the lateral dimensions of its cross section, the local magnetic field near the edges of the sample is enhanced and interacts with the shielding currents. There are many experimental (see for instance [1][2][3][4][5]) and theoretical (see for instance [6][7][8][9][10]) studies in threedimensional (3D) systems. For example, in [11], a superconducting wire with a constriction in the middle was investigated.…”