Reentrant vortex lattice transformation in four-fold symmetric superconductors

TL;DR

This paper explains the reentrant vortex lattice transformations in four-fold symmetric superconductors like LuNi₂B₂C using Eilenberger theory, revealing intrinsic competition effects and predicting new lattice lock-in transitions.

Contribution

It provides a theoretical explanation for vortex lattice reentrance and predicts a novel lock-in transition in four-fold symmetric superconductors.

Findings

Reentrant rhombic to square lattice transition explained by anisotropy competition

Theoretical reproduction of observed reentrance in LuNi₂B₂C

Prediction of a new square lattice lock-in transition at higher fields

Abstract

The physics behind the rhombic$\to$square$\to$rhombic flux line lattice transformation in increasing fields is clarified on the basis of Eilenberger theory. We demonstrate that this reentrance observed in LuNi$_2$B$_2$C is due to intrinsic competition between superconducting gap and Fermi surface anisotropies. The calculations reproduce not only it but also predict yet not found lock-in transition to a square lattice with different orientation in higher field. In view of physical origin given, this sequence of transitions is rather generic to occur in four-fold symmetric superconductors.