Quantum Antiferromagnetism of Fermions in Optical Lattices with Half-filled p-band

TL;DR

This paper demonstrates that fermions in a half-filled p-band optical lattice exhibit high-temperature antiferromagnetic order with spin-3/2, using strong coupling and mean-field theories, surpassing s-band counterparts in critical temperature.

Contribution

It reveals the emergence of spin-3/2 antiferromagnetism in p-band fermionic systems and quantifies its higher critical temperature compared to s-band systems.

Findings

Spin-3/2 antiferromagnetic order at low temperatures.

Critical temperature is about two orders of magnitude higher than s-band systems.

Antiferromagnetism confirmed via strong coupling expansion and mean-field analysis.

Abstract

We study Fermi gases in a three-dimensional optical lattice with five fermions per site, i.e. the s-band is completely filled and the p-band with three-fold degeneracy is half filled. We show that, for repulsive interaction between fermions, the system will exhibit spin-3/2 antiferromagnetic order at low temperature. This conclusion is obtained in strong interaction regime by strong coupling expansion which yields an isotropic spin-3/2 Heisenberg model, and also in weak interaction regime by Hatree-Fock mean-field theory and analysis of Fermi surface nesting. We show that the critical temperature for this antiferromagnetism of a p-band Mott insulator is about two orders of magnitudes higher than that of an $s$-band Mott insulator, which is close to the lowest temperature attainable nowadays.