Visualization of compensating currents in type-II/1 superconductor via high field cooling

Abstract

The morphology of vortex lattice domains in bulk type-II/1 superconductors is of central interest for many areas such as fundamental condensed matter physics, engineering science, and the optimization of materials for high transport current superconductivity applications. Here, we present a comprehensive experimental study of a single crystal niobium in the intermediate mixed state and Shubnikov phase with two complementary neutron techniques: high resolution polarized neutron imaging and small-angle neutron scattering. In this way, we were able to identify and visualize the occurrence of compensating currents, the flux line closure, and the freezing of the vortex spacing during the process of field cooling and high field cooling. With the combination of complementary neutron techniques, it was possible to add insights into the quest for the understanding of the flux pinning and nucleation of vortices in type-II/1 superconductors during the process of field cooling and high field cooling.