PIRSA:19040131

Quantum Many-Body Scars and Space-Time Crystalline Order from Magnon Condensation

Iadecola, T. (2019). Quantum Many-Body Scars and Space-Time Crystalline Order from Magnon Condensation. Perimeter Institute. https://pirsa.org/19040131

Iadecola, Thomas. Quantum Many-Body Scars and Space-Time Crystalline Order from Magnon Condensation. Perimeter Institute, Apr. 30, 2019, https://pirsa.org/19040131 

          @misc{ pirsa_PIRSA:19040131,
            doi = {10.48660/19040131},
            url = {https://pirsa.org/19040131},
            author = {Iadecola, Thomas},
            keywords = {Condensed Matter},
            language = {en},
            title = {Quantum Many-Body Scars and Space-Time Crystalline Order from Magnon Condensation},
            publisher = {Perimeter Institute},
            year = {2019},
            month = {apr},
            note = {PIRSA:19040131 see, \url{https://pirsa.org}}
          }

Tom Iadecola

University of Maryland, College Park

Talk number
PIRSA:19040131
Collection
Talk Type
Subject
Abstract

We study the eigenstate properties of a nonintegrable spin chain that was recently realized experimentally in a Rydberg-atom quantum simulator. In the experiment, long-lived coherent many-body oscillations were observed only when the system was initialized in a particular product state. This pronounced coherence has been attributed to the presence of special "scarred" eigenstates with nearly equally-spaced energies and putative nonergodic properties despite their finite energy density. In this paper we uncover a surprising connection between these scarred eigenstates and low-lying quasiparticle excitations of the spin chain. In particular, we show that these eigenstates can be accurately captured by a set of variational states containing a macroscopic number of magnons with momentum π. This leads to an interpretation of the scarred eigenstates as finite-energy-density condensates of weakly interacting π-magnons. One natural consequence of this interpretation is that the scarred eigenstates possess long-range order in both space and time, providing a rare example of the spontaneous breaking of continuous time-translation symmetry. We verify numerically the presence of this space-time crystalline order and explain how it is consistent with established no-go theorems precluding its existence in ground states and at thermal equilibrium.