Quantum Many-Body Scars, Magnon-Pair Condensation, and Hilbert Space Fragmentation in an Anisotropic Heisenberg Model

Abstract:We investigate a spin-$1/2$ anisotropic Heisenberg model on a lattice consisting of two identical bipartite sublattices. A family of exact eigenstates generated by the restricted spectrum generating algebra (RSGA) constitutes quantum many-body scar states, characterized by subextensive entanglement entropy and supporting. These scar states are magnon-pair condensates exhibiting off-diagonal long-range order (ODLRO). At the resonance point of the inter-sublattice interaction, the model exactly maps onto a mixed spin-$1$ and spin-$0$ XY model on a bipartite lattice, which decomposes into independent sub-Hamiltonians labeled by all possible spin configurations. Each spin-$0$ particle is dynamically isolated from its neighbors and acts as a kinetic constraint, giving rise to emergent Hilbert space fragmentation (HSF). Our work establishes an exactly solvable platform in which quantum many-body scars, magnon-pair condensation exhibiting off-diagonal long-range order, and Hilbert space fragmentation naturally coexist.

Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)

arXiv:2608.15017 [cond-mat.str-el]

(or arXiv:2608.15017v1 [cond-mat.str-el] for this version)

https://doi.org/10.48550/arXiv.2608.15017 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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