Magnetism and Hund's rule in an optical lattice with cold fermions

K. Kärkkäinen, M. Borgh, M. Manninen, S. M. Reimann

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We demonstrate that a two-dimensional (2D) optical lattice loaded with repulsive, contact-interacting fermions shows a rich and systematic magnetic phase diagram. Trapping a few (N ≤ 12) fermions in each of the single-site minima of the optical lattice, we find that the shell structure in these quantum wells determines the magnetism. In a shallow lattice, the tunnelling between the single wells is strong, and the lattice is non-magnetic (NM). For deeper lattices, however, the shell filling of the single wells with fermionic atoms determines the magnetism. As a consequence of Hund's first rule, the interaction energy is lowered by maximizing the number of atoms of the same species. This leads to a systematic sequence of NM, ferromagnetic (F) and antiferromagnetic (AF) phases.

Original languageEnglish
Article number33
JournalNew Journal of Physics
Publication statusPublished - 21 Feb 2007
Externally publishedYes

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