Quantum degenerate Fermi gas in an orbital optical lattice

TL;DR

This paper demonstrates the preparation and observation of quantum degenerate Fermi gases in excited Bloch bands of an optical lattice, revealing long lifetimes and orbital characteristics crucial for future studies of Fermi gases with spin components.

Contribution

It reports the first observation of long-lived spin-polarized and spin mixture Fermi gases in excited orbital bands of an optical lattice, with direct analysis of their orbital character.

Findings

Spin-polarized gases have lifetimes over 10 seconds.

Spin mixtures have lifetimes around one second.

Orbital character of the lattice is directly observed through momentum spectra.

Abstract

Spin-polarized samples and spin mixtures of quantum degenerate fermionic atoms are prepared in selected excited Bloch bands of an optical chequerboard square lattice. For the spin-polarized case, extreme band lifetimes above $10\,$s are observed, reflecting the suppression of collisions by Pauli's exclusion principle. For spin mixtures, lifetimes are reduced by an order of magnitude by two-body collisions between different spin components, but still remarkably large values of about one second are found. By analyzing momentum spectra, we can directly observe the orbital character of the optical lattice. The observations demonstrated here form the basis for exploring the physics of Fermi gases with two paired spin components in orbital optical lattices, including the regime of unitarity.