High-temperature surface superconductivity in rhombohedral graphite

TL;DR

This paper demonstrates that surface superconductivity in rhombohedral graphite remains robust even with higher order interlayer hoppings, leading to high critical temperatures due to increased density of states.

Contribution

It reveals that surface superconductivity in rhombohedral graphite persists with quadratic dispersion and high transition temperatures, expanding understanding beyond ideal flat band conditions.

Findings

Surface superconductivity persists despite higher order hoppings.

High critical temperature due to increased density of states.

Surface superconductivity exhibits BCS-like behavior with strong coupling.

Abstract

Surface superconductivity in rhombohedral graphite is a robust phenomenon which can exist even when higher order hoppings between the layers lift the topological protection of the surface flat band and introduce a quadratic dispersion of electrons with a heavy effective mass. We show that for weak pairing interaction, the flat band character of the surface superconductivity transforms into a BCS-like relation with high critical temperature characterized by a higher coupling constant due to a much larger density of states than in the bulk. Our results offer an explanation for the recent findings of graphite superconductivity with an unusually high transition temperature.