Superconductivity in strongly repulsive fermions: the role of kinetic-energy frustration

TL;DR

This paper proposes a non-BCS mechanism where kinetic-energy frustration stabilizes robust d-wave superconductivity in strongly repulsive fermionic systems, specifically within a modulated Hubbard model, with potential experimental realization in optical lattices.

Contribution

It introduces a novel non-BCS mechanism based on kinetic-energy frustration that enables superconductivity at arbitrarily large repulsion in a Hubbard model.

Findings

Kinetic-energy frustration can induce d-wave superconductivity.

Superconductivity persists at arbitrarily large on-site repulsion.

Potential experimental observation in optical lattices with fermionic atoms.

Abstract

We discuss a physical mechanism of a non-BCS nature which can stabilize a superconducting state in a {\it strongly repulsive} electronic system. By considering the two-dimensional Hubbard model with spatially modulated electron hoppings, we demonstrate how kinetic-energy frustration can lead to robust d-wave superconductivity at {\it arbitrarily} large on-site repulsion. This phenomenon should be observable in experiments using fermionic atoms, e.g. ${}^{40}K$, in specially prepared optical lattices.