Collective excitations in two-band superconductors

Abstract

We investigate the eigen oscillations of internal degrees of freedom (Higgs mode and Goldstone mode) of two-band superconductors using the extended time-dependent Ginzburg-Landau theory, formulated in a work Grigorishin (2021) \cite{grig2}, for the case of two coupled order parameters by both the internal proximity effect and the drag effect. It is demonstrated, that the Goldstone mode splits into two branches: common mode oscillations with the acoustic spectrum, which is absorbed by the gauge field, and anti-phase oscillations with the energy gap (mass) in the spectrum determined by the interband coupling, which can be associated with the Leggett mode. The Higgs mode splits into two branches also: a massive one, whose energy gap vanishes at the critical temperature $T_c$, another massive one, whose energy gap does not vanish at $T_c$. It is demonstrated, that the second branch of the Higgs mode is nonphysical, and it, together with the Leggett mode, can be removed by the special choice of coefficient at the "drag" term in the Lagrangian. In the same time, such a choice leaves only one coherence length, thereby prohibiting so-called type-1.5 superconductors. We analyze experimental data about the Josephson effect between two-band superconductors. In particular, it is demonstrated, that the resonant enhancement of the DC current through a Josephson junction at a resonant bias voltage $V_{\mathrm{res}}$, when the Josephson frequency matches the frequency of some internal oscillation mode in two-band superconductors (banks), can be explained with the coupling between AC Josephson current and Higgs oscillations. Thus, explanation of this effect does not need the Leggett mode.

arXiv comment17 pages, 4 figures

References in corpus (26)

• Type-1.5 Superconductors
• Semi-Meissner state and neither type-I nor type-II superconductivity in multicomponent systems
• Three-band superconductivity and the order parameter that breaks time-reversal symmetry
• Properties of the superconducting state in a two-band model
• Type-1.5 superconductivity in multiband systems: the effects of interband couplings
• Type-1.5 Superconducting State from an Intrinsic Proximity Effect in Two-Band Superconductors
• Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu${}_2$Fe${}_3$Si${}_5$
• Effective action approach to the Leggett's mode in two-band superconductors
• Specific heat and upper critical field in KFe2As2 single crystals
• Scanning SQUID microscopy of vortex clusters in multiband superconductors
• Experimental evidence of two-band behavior of MgB2
• Phenomenological Theory of Superconductivity and Magnetism in Ho${}_{1-x}$Dy${}_x$Ni${}_2$B${}_2$C
• Novel Josephson effects between multi-gap and single-gap superconductors
• Model of collective modes in three-band superconductors with repulsive interband interactions
• Superconductivity of magnesium diboride
• Phonon assisted tunneling in Josephson junctions
• Proximity and Josephson effects in microstructures based on multiband superconductors
• Coherent current states in a two-band superconductor
• Josephson currents in point contacts between dirty two-band superconductors
• Critical and non-critical coherence lengths in a two-band superconductor
• Effective Ginzburg-Landau free energy functional for multi-band isotropic superconductors
• Coherence lengths for superconductivity in the two-orbital negative-U Hubbard model
• Estimation of intraband and interband relative coupling constants from temperature dependences of the order parameter for two-gap superconductors
• Self-consistent two-gap approach in studying multi-band superconductivity in NdFeAsO${}_{0.65}$F${}_{0.35}$
• Extended time-dependent Ginzburg-Landau theory
• Correlations of superconducting fluctuations in a two-gap system

Cited by in corpus (1)

• Collective excitations in three-band superconductors