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TT: Fachverband Tiefe Temperaturen
TT 19: Focus Session: New Routes to Localization and Quantum Non-Ergodicity II (joint session TT/DY)
TT 19.7: Vortrag
Montag, 9. März 2026, 16:45–17:00, CHE/0091
Many-Body Cages - Flat bands on the state graph — •Tom Ben-Ami1, 2, Markus Heyl1, and Roderich Moessner2 — 1University of Augsburg, D-86135 Augsburg, Germany — 2Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, Dresden 01187, Germany
We identify the many-body counterpart of flat bands, which we term many-body caging, as a general mechanism for non-equilibrium phenomena such as a novel type of glassy eigenspectrum order and many-body Rabi oscillations in the time domain. We focus on constrained systems of great current interest in the context of Rydberg atoms and synthetic or emergent gauge theories. We find that their state graphs host motifs which produce flat bands in the many-body spectrum at a particular set of universal energies. Basis states in Fock space exhibit Edwards-Anderson type order in the absence of quenched disorder, with an intricate, possibly fractal, distribution over Fock space. This is reflected in a distinctive structure of a non-vanishing post-quench long-time Loschmidt echo, an experimentally accessible quantity. In general, phenomena familiar from single-particle flat bands manifest themselves in characteristic many-body incarnations, such as a reentrant ‘Anderson’ delocalisation, offering a rich ensemble of experimental signatures in the abovementioned quantum simulators. The variety of single-particle flat band types suggests an analogous typology–and concomitant phenomenological richness to be explored–of their many-body counterparts.
Keywords: non-ergodic dynamics; localization; state graphs