Dynamical vortices in electron-phonon superconductors

Abstract

We analyze the structure of an $s-$wave superconducting gap in systems with electron-phonon attraction and electron-electron repulsion. Earlier works have found that superconductivity develops despite strong repulsion, but the gap, $\Delta ({\omega }_m)$, necessarily changes sign along the Matsubara axis. We analyze the sign-changing gap function from a topological perspective using the knowledge that a nodal point of $\Delta ({\omega }_m)$ is the center of dynamical vortex. We consider two models with different cutoffs for the repulsive interaction and trace the vortex positions along the Matsubara axis and in the upper frequency half plane upon changing the relative strength of the attractive and repulsive parts of the interaction. We discuss how the presence of dynamical vortices affects the gap structure along the real axis, detectable in ARPES experiments.

arXiv comment6 pages, 5 figures

References in corpus (20)

• Topological Insulators
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Topological superconductors: a review
• A Common Thread: the pairing interaction for the unconventional superconductors
• Chiral superconductivity from repulsive interactions in doped graphene
• Nematicity and Competing Orders in Superconducting Magic-Angle Graphene
• Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point
• Eliashberg Theory: a short review
• Superconductivity in dilute SrTiO${}_3$: a review
• Metallicity and superconductivity in doped strontium titanate
• Superconductivity at very low density: the case of strontium titanate
• An organizing principle for two-dimensional strongly correlated superconductivity
• Interplay between superconductivity and non-Fermi liquid at a quantum-critical point in a metal. I: The $\gamma$-model and its phase diagram at $T=0$. The case $0<\gamma <1$
• ARPES experiment in fermiology of quasi-2D metals (Review Article)
• Phonon mediated superconductivity in low carrier-density systems
• The interplay between superconductivity and non-Fermi liquid at a quantum-critical point in a metal
• Superconductivity-induced nematicity
• Interplay between superconductivity and non-Fermi liquid at a quantum-critical point in a metal: V. The $\gamma$ model and its phase diagram. The case $\gamma =2$
• Interplay between superconductivity and non-Fermi liquid at a quantum-critical point in a metal. IV: The $\gamma$ model and its phase diagram at $1<\gamma <2$
• Implicit renormalization approach to the problem of Cooper instability