Constrain relations for superfluid weight and pairings in a chiral flat band superconductor

TL;DR

This paper derives a simple constraint relation for pairings in a chiral flat band superconductor, showing how superfluid weight and pairings depend on quantum geometry and are unaffected by lattice complexity in bipartite systems.

Contribution

It introduces a unique constraint relation for pairings in flat band superconductors with inequivalent orbitals, linking superfluid weight to quantum geometry.

Findings

Pairings obey a simple constraint relation.

Superfluid weight is controlled by half-filled lattice properties.

Lattice geometry and hopping complexity do not affect key features in bipartite systems.

Abstract

Within ten years, flat band (FB) superconductivity has gained a huge interest for its remarkable features and connection to quantum geometry. We investigate the superconductivity in a FB system whose orbitals are inequivalent and in which the gap and the quantum metric are tunable. The key feature of the present theoretical study is to show a unique and simple constrain relation that pairings obey. Furthermore, pairings and superfluid weight in partially filled FB are shown to be controlled by those of the half-filled lattice. We argue that the geometry of the lattice or the complexity of the hopping terms have no impact on the features revealed in this work as far as the system is bipartite.