Diffusive to non-ergodic dipolar transport in a dissipative atomic medium in Phys. Rev. Lett.

We highlight a well controlled experimental system for studying transport phenomena consisting of strongly interacting impurities in a Rydberg-dressed ultracold gas, which due to its long-range 1/R^3 hopping and controllable dissipation, sits at the frontiers of current theoretical understanding. The question of how an excitation propagates through an underlying medium is central to numerous domains of physics, ranging from condensed matter physics, to optical physics, quantum information, and biophysics. Often, one would like to know how this behavior is linked to the microscopic physics – such as the nature of disorder, the interactions between the particles and coupling to environmental degrees of freedom leading to decoherence – a task that is exceedingly hard to achieve in conventional materials. We show in this system that the laser fields used to observe the transport dynamics also directly controls the rate of diffusive transport. In the case where these fields are switched off completely we observe a transition to a regime in which transport effectively stops altogether which can be attributed to the system entering a highly sought after non-ergodic extended phase. Together this establishes a much needed platform for studying transport and localization phenomena spanning classical and quantum coherent limits and where all relevant degrees of freedom can be manipulated at will.

Phys. Rev. Lett. 123, 213606 (2019)