Visualizing the elongated vortices in $\gamma$-Ga nanostrips

TL;DR

This study reveals that superconducting $ ext{γ}$-Ga nanostrips exhibit highly elongated magnetic vortices due to geometric confinement, contrasting with isotropic vortices in larger samples, offering new insights into vortex behavior and potential applications.

Contribution

It demonstrates the impact of nanostrip geometry on vortex elongation in superconducting $ ext{γ}$-Ga, highlighting a novel confinement effect not previously characterized.

Findings

Vortex cores in Ga nanostrips are elongated with aspect ratios up to 40.

Elongated vortices are absent in larger, round-shaped Ga islands.

Geometric confinement and vortex-edge interactions drive the vortex elongation.

Abstract

We study the magnetic response of superconducting $\gamma$-Ga via low temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex cores rely substantially on the Ga geometry, and exhibit an unexpectedly-large axial elongation with aspect ratio up to 40 in rectangular Ga nano-strips (width $l$ $<$ 100 nm). This is in stark contrast with the isotropic circular vortex core in a larger round-shaped Ga island. We suggest that the unusual elongated vortices in Ga nanostrips originate from geometric confinement effect probably via the strong repulsive interaction between the vortices and Meissner screening currents at the sample edge. Our finding provides novel conceptual insights into the geometrical confinement effect on magnetic vortices and forms the basis for the technological applications of superconductors.