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arXiv:2609.39258

Multipartite entanglement hidden in vector-chiral correlations of spin-1/2 chains

Tokuro Shimokawa

cond-mat.str-elquant-phSubmitted Sep 30, 2026• Announced Oct 1, 2026• 0 citations
v1 · Sep 30, 2026v2 · Oct 7, 2026
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Abstract

Characterizing entanglement in quantum materials through experimentally accessible observables remains a central challenge. Quantum Fisher information associated with sums of one-site spin operators provides one route by linking entanglement to measurable magnetic response functions. Extending this approach to local composite observables requires new entanglement bounds. Here we establish a rigorous bound for the total nearest-neighbour vector chirality of periodic spin-$1/2$ chains with an even number of sites. The quantum Fisher information per spin cannot exceed $k+1$ for any $k$-producible state, so exceeding this bound certifies entanglement depth of at least $k+1$. Combining infinite density-matrix renormalization group and thermal pure quantum-state calculations, we demonstrate multipartite entanglement encoded in vector-chiral correlations at zero and finite temperatures in an extended $J_1$-$J_2$ XXZ chain. The spin-current coupling between vector chirality and electric polarization offers, in principle, access to this witness through dielectric loss spectroscopy in multiferroic magnets, extending entanglement diagnostics beyond dipolar spin correlations.

Comments
21 pages, 4 figures

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