TY - JOUR T1 - Fractal Universality in Near-Threshold Magnetic Lanthanide Dimers JF - Science Advances Y1 - 2018 A1 - Constantinos Makrides A1 - Ming Li A1 - Eite Tiesinga A1 - Svetlana Kotochigova AB -

Ergodic quantum systems are often quite alike, whereas nonergodic, fractal systems are unique and display characteristic properties. We explore one of these fractal systems, weakly bound dysprosium lanthanide molecules, in an external magnetic field. As recently shown, colliding ultracold magnetic dysprosium atoms display a soft chaotic behavior with a small degree of disorder. We broaden this classification by investigating the generalized inverse participation ratio and fractal dimensions for large sets of molecular wave functions. Our exact close-coupling simulations reveal a dynamic phase transition from partially localized states to totally delocalized states and universality in its distribution by increasing the magnetic field strength to only a hundred Gauss (or 10 mT). Finally, we prove the existence of nonergodic delocalized phase in the system and explain the violation of ergodicity by strong coupling between near-threshold molecular states and the nearby continuum.

VL - 4 U4 - eaap8308 UR - https://arxiv.org/abs/1802.09586 CP - 2 U5 - https://doi.org/10.1126/sciadv.aap8308 ER -