High-$T_c$ superconductivity of electron systems with flat bands pinned to the Fermi surface

TL;DR

This paper demonstrates that flat bands pinned to the Fermi surface can explain high-temperature superconductivity in strange metals, showing superconductivity can occur even with repulsive interactions away from critical magnetic fluctuations.

Contribution

It introduces a flat-band scenario for high-$T_c$ superconductivity based on the Landau-Pitaevskii relation, expanding understanding beyond traditional magnetic fluctuation mechanisms.

Findings

Flat bands explain properties of strange metals.

Superconductivity can occur with repulsive interactions.

Superconductivity exists away from magnetic critical lines.

Abstract

The phenomenon of flat bands pinned to the Fermi surface is analyzed on the basis of the Landau-Pitaevskii relation, which is applicable to electron systems of solids. It is shown that the gross properties of normal states of high-$T_c$ superconductors, frequently called strange metals, are adequately explained within the flat-band scenario. Most notably, we demonstrate that in electron systems moving in a two-dimensional Brillouin zone, superconductivity may exist in domains of the Lifshitz phase diagram lying far from lines of critical antiferromagnetic fluctuations, even if the effective electron-electron interaction in the Cooper channel is repulsive.