Weak ergodicity breaking from quantum many-body scars Turner, Christopher Michailidis, Alexios ; https://orcid.org/0000-0002-8443-1064 Abanin, Dmitry Serbyn, Maksym ; https://orcid.org/0000-0002-2399-5827 Papić, Zlatko The thermodynamic description of many-particle systems rests on the assumption of ergodicity, the ability of a system to explore all allowed configurations in the phase space. Recent studies on many-body localization have revealed the existence of systems that strongly violate ergodicity in the presence of quenched disorder. Here, we demonstrate that ergodicity can be weakly broken by a different mechanism, arising from the presence of special eigenstates in the many-body spectrum that are reminiscent of quantum scars in chaotic non-interacting systems. In the single-particle case, quantum scars correspond to wavefunctions that concentrate in the vicinity of unstable periodic classical trajectories. We show that many-body scars appear in the Fibonacci chain, a model with a constrained local Hilbert space that has recently been experimentally realized in a Rydberg-atom quantum simulator. The quantum scarred eigenstates are embedded throughout the otherwise thermalizing many-body spectrum but lead to direct experimental signatures, as we show for periodic recurrences that reproduce those observed in the experiment. Our results suggest that scarred many-body bands give rise to a new universality class of quantum dynamics, opening up opportunities for the creation of novel states with long-lived coherence in systems that are now experimentally realizable. Nature Publishing Group 2018 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/296 Turner C, Michailidis A, Abanin D, Serbyn M, Papić Z. Weak ergodicity breaking from quantum many-body scars. <i>Nature Physics</i>. 2018;14:745-749. doi:<a href="https://doi.org/10.1038/s41567-018-0137-5">10.1038/s41567-018-0137-5</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1038/s41567-018-0137-5 info:eu-repo/semantics/altIdentifier/wos/000438253600028 info:eu-repo/semantics/openAccess