Degenerate Landau levels for tripod-type cold atoms in U(2) Abelian gauge fieldBruno Farias, Jilvan Lemos de Melo and Claudio FurtadoEur. Phys. J. D, 68 4 (2014) 77DOI: https://doi.org/10.1140/epjd/e2014-50051-5