Effects of magnetic dipole-dipole interactions in atomic Bose-Einstein condensates with tunable s-wave interactions

The s-wave interaction is usually the dominant form of interactions in atomic Bose-Einstein condensates (BECs). Recently, Feshbach resonances have been employed to reduce the strength of the s-wave interaction in many atomic species. This opens the possibilities to study magnetic dipole-dipole interactions (MDDIs) in BECs, where the novel physics resulting from long-range and anisotropic dipolar interactions can be explored. Using a variational method, we study the effect of MDDIs on the statics and dynamics of atomic BECs with tunable s-wave interactions for a variety of species, including both nonalkali metals with large magnetic dipole moments (Cr-52, Dy-164, Er-168) and alkali metals (with much smaller magnetic dipole moments). A parameter of magnetic Feshbach resonances, epsilon(dd,max), is used to quantitatively indicate the feasibility of experimentally observing MDDI effects in different atomic species. We find that strong MDDI effects should be observable in both in-trap and time-of-flight behaviors, not only for the strongly magnetic dipolar species but also for the alkali-metal BECs of Li-7, K-39, and Cs-133. In addition, we predict several effects which should be experimentally observable. Our results provide a helpful guide for experimentalists to realize and study atomic dipolar quantum gases.