Morphology of the Superconducting Vortex Lattice in Ultra-Pure Niobium

TL;DR

This study uses small-angle neutron scattering to analyze the vortex lattice morphology in ultra-pure niobium, revealing how non-local effects, Fermi surface transitions, and mixed states influence vortex arrangements.

Contribution

It provides a comprehensive analysis of the vortex lattice in niobium, highlighting the roles of multiple mechanisms in FLL morphology and orientation.

Findings

FLL morphology varies with magnetic field orientation

Lock-in transitions and symmetry breaking observed

Multiple mechanisms influence vortex lattice structure

Abstract

The morphology of the superconducting flux line lattice (FLL) of Nb comprises gradual variations with various lock-in transitions and symmetry breaking rotations. We report a comprehensive small-angle neutron scattering study of the FLL in an ultra-pure single crystal of Nb as a function of the orientation of the applied magnetic field. We attribute the general morphology of the FLL and its orientation to three dominant mechanisms. First, non-local contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state between the Meissner and the Shubnikov phase.