Anisotropic interactions of a Rydberg impurity in a BEC

Rydberg atoms primarily interact with their environment via electron scattering, making the electronic wave function the key to the interaction potential. Tuning the principal quantum number and angular momentum allows for precise control over the interaction range, isotropy, and degeneracy, creating a highly tuneable and experimentally accessible system.

When exciting the electron to a state with angular momentum (l > 0), the spherical symmetry of the Rydberg-bath interaction breaks. We have calculated the full many-body absorption spectrum of such a Rydberg atom immersed into an ideal BEC, and from this we identify the signatures of attractive and repulsive polarons, molecules, and even classical limits. We show how the underlying two-body partial-wave scattering is governed by Feshbach type resonances and how these anisotropic interactions manifest in the absorption spectrum.