Magnetism of Cold Fermionic Atoms on p-Band of an Optical Lattice

TL;DR

This study uses ab initio methods to explore the phase diagram of spin-1/2 fermionic atoms in a p-band optical lattice, revealing a robust ferromagnetic phase and phase transitions relevant for understanding itinerant ferromagnetism.

Contribution

It provides the first ab initio analysis of ferromagnetism in cold fermionic atoms on a p-band optical lattice, highlighting the existence of a robust ferromagnetic phase over a wide parameter range.

Findings

Robust ferromagnetic phase exists across various fillings and interactions.

Transition from spin density wave to Neel state at half filling.

Spatial phase separation induced by harmonic trapping.

Abstract

We carry out \textit{ab initio} study of ground state phase diagram of spin-1/2 cold fermionic atoms within two-fold degenerate $p$-band of an anisotropic optical lattice. Using the Gutzwiller variational approach, we show that a robust ferromagnetic phase exists for a vast range of band fillings and interacting strengths. The ground state crosses over from spin density wave state to spin-1 Neel state at half filling. Additional harmonic trap will induce spatial separation of varies phases. We also discuss several relevant observable consequences and detection methods. Experimental test of the results reported here may shed some light on the long-standing issue of itinerant ferromagnetism.