Canted Antiferromagnetic Order of Imbalanced Fermi-Fermi mixtures in Optical Lattices by Dynamical Mean-Field Theory

TL;DR

This study uses Dynamical Mean-Field Theory to explore antiferromagnetic order in imbalanced Fermi-Fermi mixtures within optical lattices, revealing canted antiferromagnetism and phase separation under certain conditions.

Contribution

It provides a detailed analysis of antiferromagnetic phases in imbalanced mixtures, including boundary structures and the effects of harmonic traps, using both local density approximation and real-space DMFT.

Findings

Antiferromagnetic order is canted and perpendicular to ferromagnetic polarization.

No ferromagnetic Stoner instability is observed at moderate interactions.

Phase separation occurs only with strong imbalance and large repulsion.

Abstract

We investigate antiferromagnetic order of repulsively interacting fermionic atoms in an optical lattice by means of Dynamical Mean-Field Theory (DMFT). Special attention is paid to the case of an imbalanced mixture. We take into account the presence of an underlying harmonic trap, both in a local density approximation and by performing full Real-Space DMFT calculations. We consider the case that the particle density in the trap center is at half filling, leading to an antiferromagnetic region in the center, surrounded by a Fermi liquid region at the edge. In the case of an imbalanced mixture, the antiferromagnetism is directed perpendicular to the ferromagnetic polarization and canted. We pay special attention to the boundary structure between the antiferromagnetic and the Fermi liquid phase. For the moderately strong interactions considered here, no Stoner instability toward a ferromagnetic phase is found. Phase separation is only observed for strong imbalance and sufficiently large repulsion.