This paper reports the formation of a Mott insulator of a repulsively interacting two-component Fermi gas in an optical lattice. It is identified by three features: a drastic suppression of doubly occupied lattice sites, a strong reduction of the compressibility inferred from the response of double occupancy to an increase in atom number, and the appearance of a gapped mode in the excitation spectrum. The results pave the way for further studies of the Mott insulator, including spin-ordering and ultimately the question of d-wave superfluidity.
- Robert Jördens
- Niels Strohmaier
- Tilman Esslinger
