Slow thermalization in few-body Rydberg interactions

Through simulation, we investigate the long-time behavior of ultracold Rydberg atoms undergoing energy exchange via two-, three-, and four-body dipole-dipole interactions. Using a simplified model of atoms in a one-dimensional lattice, we calculate the entanglement entropy, level spacing statistics, and initial state survival probability. We vary the strength of the interaction by altering the lattice spacing and add disorder by randomly perturbing the positions of the atoms. While the two-body case rapidly thermalizes, we find that the three- and four-body cases exhibit slow thermalization that suggests potential non-ergodic behavior. In addition, we find that the always resonant interactions play a critical role in impeding thermalization.