Current-induced self-organisation of mixed superconducting states

Xaver S Brems,Robert Cubitt,José Albino Aguiar,Sebastian Mühlbauer,Wilmer Y Córdoba-Camacho,Alexei Vagov,Arkady A Shanenko

doi:10.1088/1361-6668/ac455e

Abstract

Small-angle neutron scattering is used in combination with transport measurements to investigate the current-induced effects on the morphology of the intermediate mixed state (IMS) domains in the intertype superconductor niobium. We report the robust self-organisation of the vortex lattice domains to elongated parallel stripes perpendicular to the applied current in a steady-state. The experimental results for the formation of the superstructure are supported by theoretical calculations, which highlight important details of the vortex matter evolution. The investigation demonstrates a mechanism of a spontaneous pattern formation that is closely related to the universal physics governing the IMS in low-κ superconductors.

Highlights

Independent of their microscopic nature superconductors (SC) are usually categorized via their response to an external magnetic field
The image shows the first order Bragg peaks stemming from the ordered flux line lattice inside the mixed state domains and the intermediate mixed state (IMS) scattering around the blacked out direct beam resulting from the magnetic contrast between Meissner state domains and mixed state domains
This work studies the evolution of the IMS domains in the IT superconductor Niobium under the influence of an external transport current using a combined small-angle neutron scattering (SANS) and transport measurement technique

Summary

Introduction

Independent of their microscopic nature superconductors (SC) are usually categorized via their response to an external magnetic field. Materials only exhibiting complete flux expulsion (Meissner state) are classified as type I, whereas materials, showing the penetration of an array of supercurrent vortices in the mixed state, are referred to as type II [1]. The intermediate mixed state (IMS), the microscopic coexistence of complete magnetic flux expulsion (Meissner state) and the penetration of an array of supercurrent vortices (mixed state), is one of the most prominent examples of IT behavior in SC and has been studied extensively in several materials [5,6,7,8,9,10]. While sharing common features with the intermediate state (IS) of type I SC, where Meissner regions coexist with normal state domains, the IMS, in contrast to the IS, can not be solely

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