Strong anisotropic transport of vortices in superconductors

Abstract

Anisotropic transport of multiple vortices is investigated by a numerical simulation method in superconductors with triangular pinning arrays. The results are discussed by means of V(I) curves, structure factor, vortex flows, and velocity noise spectrum. The dynamical phase diagram as a function of the pinning strength is obtained to characterize the motion of the vortices. The results reveal the existence of a strong transport anisotropy when the multiple vortices (dimer state) are driven in two perpendicular directions. The anisotropic behavior is interpreted in terms of the triangular geometry of the pinning arrays and the nature of the competitive interactions of vortices with periodic arrays of the pinning centers. . When an ordered vortex lattice is set in motion by a transport current, its motion gives rise to a finite electrical resistance. A promising way to immobilize the vortices is to introduce artificial pinning centers, which is efficient only in a restricted range of low temperatures and magnetic fields [7].Several efforts have been devoted to stabilize vortex motion by adjusting the pinning parameters [8][9][10][11][12][13]. A rich variety of dynamical phases occurs due to the interaction of vortices with attractive pinning sites which promote disorder on the vortex lattice [14][15][16][17][18][19]. Recent experiments have shown that the vortices could display markedly different configurations, such as multiple or giant vortex states confined in mesoscopic superconducting systems [20][21][22][23][24][25][26]. Strong caging effects result in the formation of complex vortex patterns at the interstitial region of the pinning centers [27][28][29][30]. Composite vortex ordering in the presence of periodic pinning arrays is responsible for the formation of anisotropic behavior [31-33],