Spin-orbit coupled fermions in ladder-like optical lattices at half-filling

TL;DR

This paper explores the rich phase diagram of two-component fermions in ladder-like optical lattices with spin-orbit coupling, revealing various magnetic and superconducting phases depending on interaction type and coupling strength.

Contribution

It provides a detailed analysis of phase transitions and novel phases in spin-orbit coupled fermionic ladders at half-filling, including the identification of stripe ferromagnetic and dimerized states.

Findings

Identification of Néel, rung-singlet, and ferromagnetic phases for repulsive fermions.

Discovery of striped ferromagnetic phases with Rashba-like spin-orbit coupling.

Observation of a dimerized state separating singlet superconductor and ferromagnetic phases for attractive fermions.

Abstract

We study the ground-state phase diagram of two-component fermions loaded in a ladder-like lattice at half filling in the presence of spin-orbit coupling. For repulsive fermions with unidirectional spin-orbit coupling along the legs we identify a N\'{e}el state which is separated from rung-singlet and ferromagnetic states by Ising phase transition lines. These lines cross for maximal spin-orbit coupling and a direct Gaussian phase transition between rung-singlet and ferro phases is realized. For the case of Rashba-like spin-orbit coupling, besides the rung singlet phases two distinct striped ferromagnetic phases are formed. In case of attractive fermions with spin-orbit coupling at half-filling for decoupled chains we identify a dimerized state that separates a singlet superconductor and a ferromagnetic states.