Vortex States and Phase Diagram of Multi-component Superconductors with Competing Repulsive and Attractive Vortex Interactions

TL;DR

This paper explores the complex vortex interactions and phase diagrams in multi-component superconductors like MgB2 and Fe-based materials, revealing non-monotonic behaviors and phase transitions between vortex states and the Meissner phase.

Contribution

It provides a detailed analysis of vortex interactions and phase diagrams in multi-component superconductors, highlighting conditions for attractive and repulsive vortex behaviors and phase separation phenomena.

Findings

Vortices exhibit attractive at large distances and repulsive at short distances.

Phase separation occurs between vortex clusters and the Meissner state.

The vortex behavior interpolates between type I and II superconductivity features.

Abstract

We investigate the behavior of vortices of multi-component superconductivity, realized in $\rm{MgB_2}$ and Fe-based superconductors, within the framework of Ginzburg-Landau (GL) theory in terms of numerical calculations of the time-dependent GL equations and the variational method. It is revealed that close to the critical point of the composite system the inter-component coupling makes the system behave as a single component superconductivity in most cases. However, when the bare mean-field critical points of the two components coincide with each other, and furthermore the inter-band coupling disappears at the same temperature, interesting phenomena occur as follows. Vortices interact attractively at large separation and repulsively at short distance in certain parameter space. Because of the non-monotonic interaction profile, phase separations between vortex clusters of triangular order and the Meissner state take place, which indicates a first-order phase transition associated with the penetration of the magnetic field into a superconductor sample. Phase diagrams of vortex states are then constructed with the associated magnetization curve. It is found that all these behavior interpolates the features of the type I and II superconductors.