Slow dynamics and ergodicity breaking in many-body systems

Sanjay Moudgalya

Lon Van Hove

Dong-Sheng Ding, Zhengyang Bai, Zong-Kai Liu +4 more

It is challenging to probe ergodicity breaking trends of a quantum many-body system when dissipation inevitably damages quantum coherence originated from coherent coupling and dispersive two-body interactions. Rydberg atoms provide a test bed to detect emergent exotic many-body phases and nonergodic dynamics where the strong Rydberg atom interaction competes with and overtakes dissipative effects even at room temperature. Here, we report experimental evidence of a transition from ergodic toward ergodic breaking dynamics in driven-dissipative Rydberg atomic gases. The broken ergodicity is featured by the long-time phase oscillation, which is attributed to the formation of Rydberg excitation clusters in limit cycle phases. The broken symmetry in the limit cycle is a direct manifestation of many-body collective effects, which is verified experimentally by tuning atomic densities. The reported result reveals that Rydberg many-body systems are a promising candidate to probe ergodicity breaking dynamics, such as limit cycles, and enable the benchmark of nonequilibrium phase transition.

C. M. Dai, Yunbo Zhang, X. X. Yi

Abstract Periodically driving an interacting many-body system generically leads to a featureless ergodic phase, in which the memory of initial condition is completely erased in the long time limit. Here we study the quantum East model under periodic driving, and show that the strength of the kinetic constraint can be effectively tuned by manipulating the driving amplitude when the driving frequency is high enough. Using numerical simulations, we find that there is a driving induced ergodic to non-ergodic phase transition for high frequency driving and a wide range of driving amplitude. For driven system in the non-ergodic phase, it exhibits slow dynamics and the localization of excitation. Our findings show the possibility of engineering long live Floquet states in translation-invariant quantum systems.

Pedro R. Nicácio Falcão, Adith Sai Aramthottil, Piotr Sierant +1 more

Strong disorder may significantly slow down or even completely hinder the thermalization of quantum many-body systems due to many-body localization (MBL). A sufficiently deep quasiperiodic potential may also inhibit thermalization. In this paper, we numerically demonstrate direct differences in the behavior of standard ergodicity-breaking indicators at the MBL crossover in random and quasiperiodic systems. Our key finding is the exponential increase in the sharpness of the MBL crossover with system size for quasiperiodic systems, a trend that is only linear in disordered systems. The strong tendency towards nonanalytic behavior in quasiperiodic systems is consistent with the existence of dynamical regimes with sharply defined boundaries or an MBL phase transition. It highlights the importance of quasiperiodic systems for our understanding of many-body dynamics.

Irene D’Amico