Antiferromagnetic Order of Repulsively Interacting Fermions on Optical lattices

TL;DR

This paper analyzes antiferromagnetic order in ultracold fermionic gases on optical lattices, highlighting how imbalance affects the orientation of antiferromagnetic correlations, which is crucial for experimental detection.

Contribution

It provides a theoretical analysis of antiferromagnetic order in imbalanced fermionic mixtures, revealing orientation constraints relevant for experiments.

Findings

In balanced systems, the Néel order can point in any direction.

In imbalanced mixtures, antiferromagnetism is perpendicular to the quantization axis.

Implications for experimental detection of antiferromagnetic correlations.

Abstract

The N\'eel state in fermionic mixtures of two pseudospin species in an optical lattice is analyzed at low temperatures. Experimentally it remains a challenge to demonstrate antiferromagnetic correlations in ultracold fermionic quantum gases. We find that, while in balanced systems the N\'eel order parameter can point in any spatial direction, in imbalanced mixtures antiferromagnetism is strictly perpendicular to the quantization axis (i.e., the z-axis). Since, experimentally, one always has to assume some minimal imbalance this should have important consequences for ongoing experiments.