  The effects of combined external electric and magnetic fields on elastic
collisions in ultracold Li--Rb mixtures is studied using recently obtained,
experimentally verified potentials. Our analysis provides both quantitative
predictions for and a detailed physical interpretation of the phenomena arising
from electric-field-induced interactions. It is shown that the electric field
shifts the positions of intrinsic magnetic Feshbach resonances, generates
copies of resonances previously restricted to a particular partial-wave
collision to other partial wave channels, and splits Feshbach resonances into
multiple resonances for states of non-zero angular momenta. It was recently
observed that the magnetic dipole-dipole interaction can also lift the
degeneracy of a p-wave state splitting the associated p-wave Feshbach resonance
into two distinct resonances at different magnetic fields. Our work shows that
the splitting of the resonances produced by an applied electric field is more
than an order of magnitude larger. This new phenomenon offers a complementary
way to produce and tune an anisotropic interaction and to study its effect on
the many-body physics of heteronuclear atomic gases.
