We show that an effective quadratic Zeeman effect for trapped atoms can be generated by proper laser configurations and, in particular, by the dipole trap itself. The induced quadratic Zeeman effect leads to a rich ground-state phase diagram, e.g., for a degenerate ${}^{52}\mathrm{Cr}$ gas, can be used to induce topological defects by controllably quenching across transitions between phases of different symmetries, allows for the observability of the Einstein–de Haas effect for relatively large magnetic fields, and may be employed to create $S=1∕2$ systems with spinor dynamics. Similar ideas could be explored in other atomic species opening an exciting new control tool in spinor systems.

• Received 12 December 2006

DOI:https://doi.org/10.1103/PhysRevA.75.053606