Critical superconductors

TL;DR

This paper introduces the concept of critical superconductors, where the Bogomolnyi critical point influences a broad parameter range, leading to novel topological states and distinct magnetic properties in superconducting materials.

Contribution

It extends the understanding of the Bogomolnyi critical point to a wider range of superconductors, proposing a new paradigm of critical superconductors with unique topological and magnetic features.

Findings

Identification of a critical parameter range below T_c where degeneracy is lifted

Introduction of topological equilibria in superconducting states

Relevance to modern superconducting materials

Abstract

Bogomolnyi critical point, originally introduced in string theories, is fundamental to superconductivity. At the critical temperature T_c it marks the sharp border between ideally diamagnetic bulk type-I superconductors and type-II ones that can host vortices, while itself it harbors infinitely degenerate distributions of magnetic flux in the superconducting state. Here we show that below T_c the physics of the Bogomolnyi critical point projects onto a wider range of microscopic parameters, even extremely wide for multiband superconductors. In this critical range, the degeneracy of the superconducting state at Tc is lifted into a sequence of novel topological equilibria and the customary understanding of superconducting phenomena does not suffice. As a radical departure from traditional views, we introduce the paradigm of critical superconductors, discuss their distinct magnetic properties, advocate their subdivision in terms of possible intermediate states, and demonstrate direct relevance of this paradigm to superconducting materials of prime interest today.