Vortex states inde factomesoscopic Mo₈₀Ge₂₀pentagon plates

Abstract

We present direct observations of vortex configurations in Mo 80 Ge 20 pentagonal plates using a scanning SQUID microscope. The vortex distribution tends to adapt to one of five symmetric axes in a pentagon, as expected from the sample geometry. We found that, for a vorticity of six, the vortices form a two-shell structure in a small pentagon, and a single-shell structure in a larger pentagon. We revealed how the vortex configuration is strongly modified by the presence of a pinning site at the center of the pentagon. In particular, a two-shell structure is formed in the pinning-site sample with a vorticity of L = 4, while the second shell appeared in the pinning site-free sample with a vorticity up to L = 6. Furthermore, upon geometric confinement, the vortices attempt to form a symmetrical configuration reflecting the sample geometry even in the presence of a pinning site (or sites). The experimental results for pentagons are in good agreement with our theoretical predictions based on the nonlinear Ginzburg-Landau equation both for a pin-free pentagon and a pentagon with a pin at the center.

Finite-size effect of critical penetration of Pearl vortices in narrow superconducting flat rings

“…2 The interplay between the intervortex interaction and the confinement results in unique vortex states, different from the Abrikosov-vortex lattice in bulk superconductors. These include vortex polygons, 3 concentric vortex shells, 4,5 and vortex fusion, [6][7][8][9] which have been directly observed in imaging experiments on small superconducting discs, 10,11 squares, 12,13 , triangles, 14,15 pentagons, 16 and others. [17][18][19] In recent years there has been renewed interest in vortices trapped in small superconductors as one of the control sources for non-equilibrium excess quasiparticles.…”

Vortex shells in mesoscopic triangles of amorphous superconducting thin films

“…The issue of vortex shells would be interesting when vortices are confined in polygonal small superconductors like triangle [8,9,10], square [11,12] and pentagonal shaped dots [13]. These polygonal dots have discrete, natural symmetries that coincide or compete with the configurational symmetry of vortex polygons, depending on vorticity L. In triangle dots, vortices intrinsically form a triangular cluster of which symmetry is commensurate with that of the triangle geometry.…”

Scanning SQUID Microscope for Sensing Vector Magnetic Field

“…Scanning SQUID microscopy is considered as a useful tool for mapping a local magnetic field by scanning a pick-up coil connected to a SQUID readout circuit. The SQUID devices are useful in various fields such as magnetics, electronics, biology, spintronics, security analysis, agriculture, information technology, communication, and physics [3,4,5]. A conventional scanning SQUID microscope can observe the distribution of local magnetic field by scanning a single coil which is able to sense a magnetic field only along the Z direction.…”