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arXiv · 2410.22773

Exact volume-law entangled zero-energy eigenstates in a large class of spin models

Sashikanta Mohapatra·Sanjay Moudgalya·Ajit C. Balram
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Abstract

Exact solutions for excited states in non-integrable quantum Hamiltonians have revealed novel dynamical phenomena that can occur in quantum many-body systems. This work proposes a method to analytically construct a specific set of volume-law-entangled zero-energy exact excited eigenstates in a large class of spin Hamiltonians. In particular, we show that all spin chains that satisfy a simple set of conditions host exact volume-law zero-energy eigenstates in the middle of their spectra. Examples of physically relevant spin chains of this type include the transverse-field Ising model, PXP model, spin-$S$ $XY$ model, and spin-$S$ Kitaev chain. Although these eigenstates are highly atypical in their structure, they are thermal with respect to local observables. Our framework also unifies many recent constructions of volume-law entangled eigenstates in the literature. Finally, we show that a similar construction also generalizes to spin models on graphs in arbitrary dimensions.

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Sashikanta Mohapatra, Sanjay Moudgalya, Ajit C. Balram. 2024-10-30. Exact volume-law entangled zero-energy eigenstates in a large class of spin models. https://doi.org/10.1103/physrevlett.134.210403

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