Leggett mode in a strong-coupling model of iron arsenide superconductors

Abstract

Using a two-orbital model of the superconducting phase of the pnictides, we compute the spectrum of the Leggett mode -- a collective excitation of the phase of the superconducting gap known to exist in multi-gap superconductors -- for different possible symmetries of the superconducting order parameter. Specifically, we identify the small regions of parameter space where the Leggett mode lies below the two-particle continuum, and hence should be visible as a sharp resonance peak. We discuss the possible utility of the Leggett mode in distinguishing different momentum dependencies of the superconducting gap. We argue that the observation of a sharp Leggett mode would be consistent with the presence of strong electron-electron correlations in iron-based superconductors. We also emphasize the importance of the orbital character of the Leggett mode, which can result in an experimental observation of the mode in channels other than $A_{1g}$.

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• Length scales, collective modes, and type-1.5 regimes in three-band superconductors
• Massless Leggett Mode in Three-band Superconductors with Time-Reversal-Symmetry Breaking
• Collective Excitations and Nonequilibrium Phase Transition in Dissipative Fermionic Superfluids
• Nonlinear optical response of collective modes in multiband superconductors assisted by nonmagnetic impurities
• Leggett modes in iron-based superconductors as a probe of Time Reversal Symmetry Breaking
• Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors
• Model of collective modes in three-band superconductors with repulsive interband interactions
• Ground state, collective mode, phase soliton and vortex in multiband superconductors
• Collective modes in multiband superfluids and superconductors: Multiple dynamical classes
• Distinguishing between $s+id$ and $s+is$ pairing symmetries in multiband superconductors through spontaneous magnetization pattern induced by a defect
• Optical response of the Leggett mode in multiband superconductors in the linear response regime
• Strong interaction between electrons and collective excitations in multiband superconductor MgB2
• Massless collective excitations in frustrated multi-band superconductors
• Classification of Lifshitz invariant in multiband superconductors: an application to Leggett modes in the linear response regime in Kagome lattice models
• Fluctuations and pairing in Fe-based superconductors: Light scattering experiments
• Superconducting Order Parameters in overdoped BaFe${}_{1.86}$Ni${}_{0.14}$As${}_2$ Revealed by Multiple Andreev Reflection Spectroscopy of Planar Break-Junctions
• Evidence of a multiple boson emission in Sm${}_{1-x}$Th${}_x$OFeAs
• Optically active Higgs and Leggett modes in multiband pair-density-wave superconductors with Lifshitz invariant
• Direct observation of the spin exciton in Andreev spectroscopy of iron-based superconductors