Commensurability effects in the critical forces of a superconducting film with Kagomé pinning array at submatching fields

Abstract

Using molecular dynamics simulations, we find the commensurability force peaks in a twodimensional superconducting thin-film with a Kagomé pinning array. A transport force is applied in two mutually perpendicular directions, and the magnetic field is increased up to the first matching field. Usually the condition to have pronounced force peaks in systems with periodic pinning is associated to the rate between the applied magnetic field and the first matching field, it must be an integer or a rational fraction. Here, we show that another condition must be satisfied, the vortex ground state must be ordered. Our calculations show that the pinning size and strength may dramatically change the vortex ground state. Small pinning radius and high values of pinning strength may lead to disordered vortex configurations, which fade the critical force peaks. The critical forces show anisotropic behavior, but the same dependence on pinning strength and radius is observed for both driven force directions. Different to cases where the applied magnetic field is higher than the first matching field, here the depinning process begins with vortices weakly trapped on top of a pinning site and not with interstitial vortices. Our results are in good agreement with recent experimental results.

Vortex Dynamic Phases in Type II Superconducting Strips with Regular and Flattened Triangular Pinning Arrays

“…Our calculations show that there are several vortex transient motions below the depinning current (region I), which can be seen by small fluctuations in the differential resistance curve. A similar type of transient motion was already reported before in simulations with infinite samples [65][66][67]. This kind of motion reorders the vortex lattice into a new static one.…”

Surface Effects on the Dynamic Behavior of Vortices in Type II Superconducting Strips with Periodic and Conformal Pinning Arrays

“…The second term on the right is the vortex-pinning interaction, which is described as a Gaussian function [32,33,37,54,77]:…”

“…The average vortex velocity is proportional to the macroscopically measured voltage-current curve [15,54]. The criterion used to determine the depinning forces is that V < 0.001 corresponds to vortex fluctuations around the equilibrium position [33,37]. For the characterization Fig.…”

“…For periodic pinning, such as square [12][13][14][15][16][17][18][19][20][21], triangular [30][31][32][33][34][35]55], honeycomb [27,29,30,38], and Kagomé [27-29, 32, 37], vortices tend to match the pinning lattice in commensurate patterns, which greatly enhances the critical current density. However, these enhancements occur at specific values of magnetic fields, resulting in high oscillations of the critical current as a function of the applied field [13,14,29,[33][34][35][36][37][38][39][40]. On the other hand, quasiperiodic arrays, such as Penrose [43,44,48], hyperbolic tessellations [47], and Archimedean tilings [41,46], show unusual commensurability effects for several values of applied magnetic fields; besides that, for a wide range of fields, the critical depinning currents are high.…”

Stability of degenerate vortex states and multi-quanta confinement effects in a nanostructured superconductor with Kagome lattice of elongated antidots

“…In this work, we explore the multi-quanta confinement effects in a nanostructured superconducting film that is divided into periodic but sufficiently isolated hexagonal areas. The issue is motivated from the recent works, where some unique physical properties have been observed in superconductors with complex pinning landscapes, such as honeycomb and Kagome patterns [43][44][45]. The well-designed structures provide opportunities to explore complex but fascinating physical phenomena.…”