Title:	Superconducting-magnetic hybrid structures
DNr:	NAISS 2024/5-146
Project Type:	NAISS Medium Compute
Principal Investigator:	Tomas Lofwander <tomas.lofwander@chalmers.se>
Affiliation:	Chalmers tekniska högskola
Duration:	2024-03-27 – 2025-04-01
Classification:	10304
Keywords:

Abstract

Our group has has developed a finite-element solver for the quasiclassical theory of superconductivity. It can be used to simulate equilibrium properties and transport in two-dimensional (2D) superconducting systems. The underlying code is in C++, uses the open-source deal.ii library, and is highly parallelized through e.g. the PETSc library of matrix-equation solvers. More recently, this work has been extended to be able to treat systems with non-trivial spin degree of freedom. This project aims to study the interplay of magnetic materials featuring skyrmions, meaning non-trivially winding magnetic fields, and superconductors. Experimental studies[1] on bilayer structures of these two types of materials have found evidence for the creation of vortex-antivortex pairs inside the superconducting layer and the occurence of coupled (anti)vortex-skyrmion excitations. The interpretation of these experiments, based on a Ginzburg-Landau framework, is that antivortex creation is energetically favourable. The underlying theory is, however, only valid close to the superconducting critical temperature. We want to study the energetics of such vortex/antivortex-skyrmion pairs within the quasiclassical theory of superconductivity. This allows for both lower temperatures and e.g. for varying mean free path in the superconductor. We can therefore study parts of the parameter space where the intricate physics of such exotic hybrid structures is, for now, not understood. References: [1] Petrovic et. al., PRL 126, 117205 (2021)