Two-band superconductors: Hidden criticality deep in the superconducting state

Abstract

We show that two-band superconductors harbor hidden criticality deep in the superconducting state, stemming from the critical temperature of the weaker band taken as an independent system. For sufficiently small interband coupling $\gamma$ the coherence length of the weaker band exhibits a remarkable deviation from the conventional monotonic increase with temperature, namely, a pronounced peak close to the hidden critical point. The magnitude of the peak scales proportionally to γ^(-μ), with the Landau critical exponent μ= 1/3, the same as found for the mean-field critical behavior with respect to the source field in ferromagnets and ferroelectrics. Here reported hidden criticality of multi-band superconductors can be experimentally observed by, e.g., imaging of the variations of the vortex core in a broader temperature range. Similar effects are expected for the superconducting multilayers.

6 pages, 2 figures, Supplementary material included. Accepted for publication in PRL

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• Band-edge BCS-BEC crossover in a two-band superconductor: physical properties and detection parameters
• Emergent phenomena in multicomponent superconductivity: an introduction to the focus issue
• Stability of fractional vortex states in a two-band mesoscopic superconductor
• Ground state, collective mode, phase soliton and vortex in multiband superconductors
• Dissociation Transition of a Composite Lattice of Magnetic Vortices in the Flux-Flow Regime of Two-Band Superconductors
• Stabilizing fractional vortices in multiband superconductors with periodic pinning arrays
• Topological phase transitions in small mesoscopic chiral p-wave superconductors
• Locking of length scales in two-band superconductors
• Type-1.5 superconductivity in muliband and other multicomponent systems
• Correlations of superconducting fluctuations in a two-gap system
• Extended Uniform Ginzburg-Landau Theory for Novel Multiband Superconductors