Superconductivity of repulsive spinless fermions with sublattice potentials

TL;DR

This paper investigates unconventional superconductivity in repulsive spinless fermions on square and honeycomb lattices with sublattice potentials, revealing diverse pairing symmetries and topological phases through analytical and numerical methods.

Contribution

It uncovers new superconducting phases, including topological $p+ip$ pairing, driven by sublattice potentials and doping, using a combination of analytical and advanced numerical techniques.

Findings

Staggered $d$-wave and $f$-wave pairing identified at low doping.

Topological $p+ip$ superconductivity emerges at higher doping on the square lattice.

Rich phase diagrams with multiple superconducting phases derived from FRG and DMRG calculations.

Abstract

We explore unconventional superconductivity of repulsive spinless fermions on square and honeycomb lattices with staggered sublattice potentials. The two lattices can exhibit staggered $d$-wave and $f$-wave pairing, respectively, at low doping stemming from an effective two-valley band structure. At higher doping, in particular, the square lattice displays a much richer phase diagram including topological $p+ip$ superconductivity which is induced by a qualitatively different mechanism compared to the $d$-wave pairing. We illuminate this from several complementary perspectives: We analytically perform sublattice projection to analyze the effective continuum low-energy description and we numerically calculate the binding energies for pair and larger bound states for few-body doping near half filling. Furthermore, for finite doping, we present phase diagrams based on extensive functional renormalization group and and density matrix renormalization group calculations.