Unconventional vortex states in nanoscale superconductors due to shape-induced resonances in the inhomogeneous Cooper-pair condensate

TL;DR

This paper demonstrates that in nanoscale superconductors, shape-induced resonances in the order parameter lead to unconventional vortex configurations, including asymmetric and multi-vortex states, differing from traditional Ginzburg-Landau predictions.

Contribution

It introduces the impact of shape resonances on vortex states in nanoscale superconductors, revealing novel configurations beyond standard theories.

Findings

Discovery of asymmetric vortex structures

Identification of giant multi-vortex states

Presence of vortex-antivortex configurations

Abstract

Vortex matter in mesoscopic superconductors is known to be strongly affected by the geometry of the sample. Here we show that in nanoscale superconductors with coherence length comparable to the Fermi wavelength the shape resonances of the order parameter results in an additional contribution to the quantum topological confinement - leading to unconventional vortex configurations. Our Bogoliubov-de Gennes calculations in a square geometry reveal a plethora of asymmetric, giant multi-vortex, and vortex-antivortex structures, stable over a wide range of parameters and which are very different from those predicted by the Ginzburg-Landau theory. These unconventional states are relevant for high-Tc nanograins, confined Bose-Einstein condensates, and graphene flakes with proximity-induced superconductivity.