Formation of quantum scars in many-body systems provides a novel mechanism for enhancing coherence of weakly entangled states. At the same time, coherence of edge modes in certain symmetry protected topological (SPT) phases can persist away from the ground state. In this work we show the existence of many-body scars and their implications on bulk coherence in such an SPT phase. To this end, we study the eigenstate properties and the dynamics of an interacting spin-$1/2$ chain with three-site "cluster" terms hosting a $\mathbb{Z}_2 \times \mathbb{Z}_2$ SPT phase. Focusing on the weakly interacting regime, we find that eigenstates with volume-law entanglement coexist with area-law entangled eigenstates throughout the spectrum. We show that a subset of the latter can be constructed by virtue of repeated cluster excitations on the even or odd sublattice of the chain, resulting in an equidistant "tower" of states, analogous to the phenomenology of quantum many-body scars. We further demonstrate that these scarred eigenstates support nonthermal expectation values of local cluster operators in the bulk and exhibit signatures of topological order even at finite energy densities. Studying the dynamics for out-of-equilibrium states drawn from the noninteracting "cluster basis", we unveil that nonthermalizing bulk dynamics can be observed on long time scales if clusters on odd and even sites are energetically detuned. In this case, cluster excitations remain essentially confined to one of the two sublattices such that inhomogeneous cluster configurations cannot equilibrate and thermalization of the full system is impeded. Our work sheds light on the role of quantum many-body scars in preserving SPT order at finite temperature and the possibility of coherent bulk dynamics in models with SPT order beyond the existence of long-lived edge modes.
Symmetry protected quantum many body scars through half-gauging
Okinawa Institute of Science and Technology Graduate University（冲绳科学技术大学院大学）；National Tsing Hua University（国立清华大学）；National Center for Theoretical Sciences（国家理论科学中心）；Academia Sinica（中央研究院）
Systematic construction of quantum many-body scars in frustrated Rydberg arrays
Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究所）；Physics Department, Technical University of Munich, TUM School of Natural Sciences（慕尼黑工业大学自然科学学院物理系）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
Additional quantum many-body scars of the spin-$1$ $XY$ model with Fock-space cages and commutant algebras
Institute of Mathematical Sciences（马哈拉施特拉数学科学研究所）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；Technische Universität München (TUM)（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
Quantum synchronization and chimera states in a programmable quantum many-body system
RIKEN Center for Emergent Matter Science (CEMS)（RIKEN 涌现物质科学中心）；RIKEN Center for Quantum Computing (RQC)（RIKEN 量子计算中心）；RIKEN Center for Computational Science (R-CCS)（RIKEN 计算科学中心）；RIKEN Cluster for Pioneering Research (CPR)（RIKEN 先锋研究集群）
