Antiferromagnetic Spin Correlation of SU(N) Fermi Gas in an Optical Superlattice.

Large-spin cold atomic systems can exhibit unique phenomena that do not appear in spin-1/2 systems. We report the observation of nearest-neighbor antiferromagnetic spin correlations of a Fermi gas with SU(N) symmetry trapped in an optical lattice. The precise control of the spin degrees of freedom provided by an optical pumping technique enables us a straightforward comparison between the cases of SU(2) and SU(4). Our important finding is that the antiferromagnetic correlation is enhanced for the SU(4)-spin system compared with SU(2) as a consequence of a Pomeranchuk cooling effect. This work is an important step towards the realization of novel SU(N>2) quantum magnetism.