Pi-phases in balanced fermionic superfluids on spin-dependent optical lattices

TL;DR

This paper investigates modulated pairing states, similar to pi-phases, in a balanced ultracold fermionic system with spin-dependent optical lattices, revealing sharp transitions and stability against phase separation.

Contribution

It introduces and analyzes pi-phase-like states in a balanced fermionic superfluid with spin-dependent lattices, highlighting their stability and transition behavior.

Findings

States with modulated order parameters similar to pi-phases are found.

Increasing lattice depth causes sharp parity transitions.

The system remains stable against phase separation despite order parameter oscillations.

Abstract

We study a balanced two-component system of ultracold fermions in one dimension with attractive interactions and subject to a spin-dependent optical lattice potential of opposite sign for the two components. We find states with different types of modulated pairing order parameters which are conceptually similar to pi-phases discussed for superconductor-ferromagnet heterostructures. Increasing the lattice depth induces sharp transitions between states of different parity. While the origin of the order parameter oscillations is similar to the FFLO phase for paired states with spin imbalance, the current system is intrinsically stable to phase separation. We discuss experimental requirements for creating and probing these novel phases.