Superconducting-magnetic hybrid structures

Dnr:

NAISS 2024/5-146

Type:

NAISS Medium Compute

Principal Investigator:

Tomas Lofwander

Affiliation:

Chalmers tekniska hÃ¶gskola

Start Date:

2024-03-27

End Date:

2025-04-01

Primary Classification:

10304: Condensed Matter Physics

Webpage:

- Centre Storage at NSC: 500 GiB
- Tetralith at NSC: 75 x 1000 core-h/month

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)