Visualizing the elongated vortices in γ -Ga nanostrips

We study the magnetic response of superconducting γ -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 nanostrips (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.