Hybridization and interference effects for localized superconducting states in strong magnetic field

TL;DR

This paper investigates how hybridization and interference of superconducting channels along edges and domain walls in thin-film ferromagnetic-superconducting bilayers can enhance the critical temperature and create localized superconducting states under strong magnetic fields.

Contribution

It introduces a model for the hybridization of order parameter modes along crossing channels and analyzes their impact on critical temperature enhancement using variational and numerical methods.

Findings

Critical temperature increases near crossing points of channels.

Hybridized order parameter modes form vortex chains.

Wave function squeezing leads to localized superconductivity.

Abstract

Within the Ginzburg-Landau model we study the critical field and temperature enhancement for crossing superconducting channels formed either along the sample edges or domain walls in thin-film magnetically coupled superconducting - ferromagnetic bilayers. The corresponding Cooper pair wave function can be viewed as a hybridization of two order parameter (OP) modes propagating along the boundaries and/or domain walls. Different momenta of hybridized OP modes result in the formation of vortex chains outgoing from the crossing point of these channels. Near this crossing point the wave functions of the modes merge giving rise to the increase in the critical temperature for a localized superconducting state. The origin of this critical temperature enhancement caused by the wave function squeezing is illustrated for a limiting case of approaching parallel boundaries and/or domain walls. Using both the variational method and numerical simulations we have studied the critical temperature dependence and OP structure vs the applied magnetic field and the angle between the crossing channels.