Multichannel quantum-defect theory (MQDT) provides a powerful toolkit for describing and understanding collisions of cold alkali-metal atoms. Various MQDT approximations differ primarily in how they characterize the so-called short-ranged K matrix Ksr, which encapsulates the short-ranged physics into a handful of low-energy parameters that exhibit simple and smooth dependence on energy and field. Here, we compare three different methods for computing Ksr for homonuclear collisions of alkali-metal atoms, from lithium to cesium. The MQDT calculations are benchmarked against numerically converged coupled-channels calculations that use a log-derivative propagator out to the asymptotic region. We study how well these approximations reproduce positions of s-wave magnetic Feshbach resonances, comparing with experiment where possible, and identify the limitations of various approximations.
American Physical Society
Laskowski, A., & Mehta, N. P. (2023). Homonuclear ultracold elastic s-wave collisions of alkali-metal atoms via multichannel quantum defect theory. Physical Review A, 108(4), Article 043306. https://doi.org/10.1103/PhysRevA.108.043306
Physical Review A