Degenerate Landau levels for tripod-type cold atoms in U(2) Abelian gauge field Bruno Farias, Jilvan Lemos de Melo and Claudio Furtado Eur. Phys. J. D, 68 4 (2014) 77 Published online: 15 April 2014 DOI: 10.1140/epjd/e2014-50051-5