Current-induced Self-organisation of Mixed Superconducting States

In the elemental superconductor Niobium we observe in the intermediate mixed state the coexistence of flux-free Meissner state domains and domains filled with vortices, called mixed state domains. Besides being a prominent example of superconducting vortex matter, the IMS can also act as a highly tunable model system for universal domain physics [1].

Vortices in a superconductor can be depinned using a transport current resulting in the flux flow state: For currents higher than the depinning current I_c vortices move orthogonal to the direction of the applied current. In contrast to the canonical mixed state, non-trivial ordering phenomena are expected in the flux flow regime of the IMS due to its highly heterogeneous domain structure. In a recent study [2] combining transport measurements and small-angle neutron scattering (SANS) on a Nb single crystal sample we could verify the existence of the IMS in the state of flux flow. Our main result is an observation of a transition from isotropic to anisotropic IMS scattering indicating that the IMS rearranges itself into a stripe superstructure in the flux flow regime. The stripe pattern is aligned perpendicular to the current direction along the motion of the vortices.

[1] M. Seul and D. Andelman 1995 Science 267(5197):476–483

[2] Xaver S Brems et al 2022 Supercond. Sci. Technol. 35 035003