Density-Wave and Antiferromagnetic States of Fermionic Atoms in Optical Lattices

TL;DR

This study investigates how two-band effects influence phase transitions in ultracold fermionic atoms in optical lattices, revealing the emergence of density-wave and antiferromagnetic states and their transitions to superfluid and metallic states.

Contribution

It provides a detailed phase diagram at half-filling considering two-band effects and orbital splitting, using dynamical mean-field theory and an effective boson model.

Findings

ADW state emerges in attractive interactions at half-filling.

Antiferromagnetic state appears in repulsive interactions.

Quantum phase transitions occur with increasing orbital splitting.

Abstract

We study the two-band effects on ultracold fermionic atoms in optical lattices by means of dynamical mean-field theory. We find that at half-filling the atomic-density-wave (ADW) state emerges owing to the two-band effects in the attractive interaction region, while the antiferromagnetic state appears in the repulsive interaction region. As the orbital splitting is increased, the quantum phase transitions from the ADW state to the superfluid state and from the antiferromagnetic state to the metallic state occur in respective regions. Systematically changing the orbital splitting and the interaction, we obtain the phase diagram at half-filling. The results are discussed using the effective boson model derived for the strong attractive interaction.