Complex state induced by impurities in multiband superconductors

Abstract

We study the role of impurities in a two-band superconductor, and elucidate the nature of the recently predicted transition from s_{+-} state to s_{++} state induced by interband impurity scattering. Using a Ginzburg-Landau theory, derived from microscopic equations, we demonstrate that close to T_c this transition is necessarily a direct one, but deeper in the superconducting state an intermediate complex state appears. This state has a distinct order parameter, which breaks the time-reversal symmetry, and is separated from the s_{+-} and s_{++} states by phase transitions. Based on our results, we suggest a phase diagram for systems with weak repulsive interband pairing, and discuss its relevance to iron-based superconductors.

7 pages, 4 figures, several typos fixed, Fig 1 replaced

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• Properties of dirty two-bands superconductors with repulsive interband interaction: normal modes, length scales, vortices and magnetic response
• Frustration phenomena in Josephson point contacts between single-band and three-band superconductors
• Supercurrent rectification with time-reversal symmetry broken multiband superconductors
• Dc SQUID based on a three-band superconductor with broken time-reversal symmetry
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• Spontaneous time-reversal symmetry breaking by disorder in superconductors
• Phase diagram of dirty two-band superconductors and observability of impurity-induced $s+is$ state
• Magneto-topological transitions in multicomponent superconductors
• Signatures of triplet correlations in density of states of Ising superconductors
• General theory of robustness against disorder in multi-band superconductors
• Josephson systems based on ballistic point contacts between single-band and multi-band superconductors
• Green function theory of dirty two-band superconductivity
• Time-reversal symmetry breaking state in dirty three-band superconductor
• Supercurrent Diode Effect in Josephson Interferometers with Multiband Superconductors
• Inhomogeneous magnetic multiband superconductors
• Change of the vortex core structure in two-band superconductors at impurity-scattering-driven $s_{\pm }/s_{++}$ crossover
• Field-induced coexistence of $s_{++}$ and $s_{\pm }$ superconducting states in dirty multiband superconductors
• Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution ARPES