Orbital phases of fermions in an asymmetric optical ladder

TL;DR

This paper investigates a quantum ladder model of interacting fermions with s and p orbitals, revealing a complex phase diagram with exotic superconducting phases, including superconductivity under repulsive interactions, using bosonization techniques.

Contribution

It introduces a novel model of fermions in an optical ladder with coupled orbitals, analyzing its rich phase diagram and discovering unconventional superconducting phases.

Findings

Identification of incommensurate orbital density wave phase

Discovery of pair density wave and exotic superconducting phases

Superconductivity observed even in the presence of repulsive interactions

Abstract

We study a quantum ladder of interacting fermions with coupled s and p orbitals. Such a model describes dipolar molecules or atoms loaded into a double-well optical lattice, dipole moments being aligned by an external field. The two orbital components have distinct hoppings. The tunneling between them is equivalent to a partial Rashba spin-orbital coupling when the orbital space (s, p) is identified as spanned by pseudo-spin 1/2 states. A rich phase diagram, including incommensurate orbital density wave, pair density wave and other exotic superconducting phases, is proposed with bosonization analysis. In particular, superconductivity is found in the repulsive regime.