Unconventional Pairing in Doped Band Insulators on a Honeycomb Lattice : the Role of the Disconnected Fermi Surface and a Possible Application to Superconducting $\beta$-MNCl (M=Hf,Zr)

TL;DR

This paper explores how disconnected Fermi surfaces in doped honeycomb lattice insulators can lead to unconventional superconductivity, with potential applications to layered nitrides like $eta$-MNCl, and compares them to iron pnictides.

Contribution

It proposes a new mechanism for unconventional superconductivity based on Fermi surface disconnectivity and applies it to doped layered nitrides, highlighting similarities with iron pnictides.

Findings

Disconnected Fermi surfaces facilitate unconventional pairing.

Layered nitrides $eta$-MNCl are promising superconductors.

Comparison shows high $T_c$ in disconnected Fermi surface materials.

Abstract

We investigate the possibility of realizing unconventional superconductivity in doped band insulators on the square lattice and the honeycomb lattice, where the latter is found to be a good candidate due to the disconnectivity of the Fermi surface. We propose applying the theory to the superconductivity in doped layered nitride $\beta$-$M$NCl ($M=$Hf, Zr). Finally, we compare two groups of superconductors with disconnected Fermi surface, $\beta$-$M$NCl and the iron pnictides, which have high $T_c$ despite some faults against superconductivity are present.