Critical depinning force and vortex lattice order in disordered superconductors

Abstract

We simulate the ordering of vortices and its effects on the critical current in superconductors with varied vortex-vortex interaction strength and varied pinning strengths for a two-dimensional system. For strong pinning the vortex lattice is always disordered and the critical depinning force only weakly increases with decreasing vortex-vortex interactions. For weak pinning the vortex lattice is defect free until the vortex-vortex interactions have been reduced to a low value, when defects begin to appear with a simultaneous rapid increase in the critical depinning force. In each case the depinning force shows a maximum for non-interacting vortices. The relative height of the peak increases and the peak width decreases for decreasing pinning strength in excellent agreement with experimental trends associated with the peak effect. We show that scaling relations exist between the distance between defects in the vortex lattice and the critical depinning force.

Mapping degenerate vortex states in a kagome lattice of elongated antidots via scanning Hall probe microscopy

“…The appeal and advantage of superconducting systems is that the size and number of the particles can be tuned by changing the temperature and the magnetic field, respectively. In addition, the flexibility in the design and fabrication of artificial vortex traps in superconducting films has stimulated, during the past decade, an in-depth investigation of the interplay between pinning landscape and vortex pattern symmetry [16], influence of the pinning center's size and period [17][18][19][20], vortex rectification on a kagome-like array [21], competition between ordered and disordered defects [22][23][24], or pinning energy dispersion [25,26], to name a few.…”

Disordering transitions and peak effect in polydisperse particle systems

“…An open question is how quenched disorder affects a dispersity-driven amorphization process and how the amorphization might alter the pinning effectiveness. A stiff lattice is poorly pinned by random disorder, and thus in a monodisperse assembly of repulsively interacting particles on quenched random disorder, the depinning threshold decreases when the lattice is stiffened by increasing the repulsion between the particles 16 . A similar decrease of the depinning threshold with increasing particle-particle interactions occurs even when the monodisperse system contains some topological disorder and is no longer a perfect elastic lattice 16 .…”

“…A stiff lattice is poorly pinned by random disorder, and thus in a monodisperse assembly of repulsively interacting particles on quenched random disorder, the depinning threshold decreases when the lattice is stiffened by increasing the repulsion between the particles 16 . A similar decrease of the depinning threshold with increasing particle-particle interactions occurs even when the monodisperse system contains some topological disorder and is no longer a perfect elastic lattice 16 . The situation may be different in a bidisperse system where the relative strength of the repulsive interactions between the two particle species can be independently tuned.…”

Ginzburg-Landau theory of type II superconductors in magnetic field

“…To address the last problem another simplified model had been proven to be more convenient: the elastic medium approach to a collection of interacting line-like objects subject to both the pinning potential and the thermal bath Langevin force (Cha and Fertig, 1994a,b;Dodgson et al, 2000;Faleski et al, 1996;Fangohr et al, 2001Fangohr et al, , 2003Olson et al, 2001;Reichhardt et al, 1996Reichhardt et al, , 2000van Otterlo et al, 1998). The resulting theory was treated again using the gaussian approximation (Giamarchi and Le Doussal, 1994, 1997Korshunov, 1993) and RG (Bogner et al, 2001;Nattermann, 1990;Nattermann and Scheidl, 2000).…”