Investigation of entanglement measures across the magnetization process of a highly frustrated spin-1/2 Heisenberg octahedral chain as a new paradigm of the localized-magnon approach

TL;DR

This paper explores bipartite entanglement in a frustrated spin-1/2 Heisenberg octahedral chain using localized magnons, demonstrating high-precision predictions and revealing entanglement behavior across different magnetic phases.

Contribution

It introduces a new paradigm for calculating entanglement measures using localized magnons in a frustrated quantum spin chain.

Findings

Localized-magnon theory accurately predicts bipartite entanglement at low temperatures.

Different magnetic phases show distinct entanglement patterns between spins.

Exact diagonalization confirms the theory's high precision in finite systems.

Abstract

The bipartite entanglement across the magnetization process of a highly frustrated spin-1/2 Heisenberg octahedral chain is examined within the concept of localized magnons, which enables a simple calculation of the concurrence measuring a strength of the pairwise entanglement between nearest-neighbor and next-nearest-neighbor spins from square plaquettes. A full exact diagonalization of the finite-size Heisenberg octahedral chain with up to 4 unit cells (20 spins) evidences an extraordinary high precision of the localized-magnon theory in predicting measures of the bipartite entanglement at sufficiently low temperatures. While the monomer-tetramer phase emergent at low enough magnetic fields exhibits presence (absence) of the bipartite entanglement between the nearest-neighbor (next-nearest-neighbor) spins, the magnon-crystal phase emergent below the saturation field contrarily displays identical bipartite entanglement between the nearest-neighbor and next-nearest-neighbor spins. The presented results verify a new paradigm of the localized-magnon approach concerned with a simple calculation of entanglement measures.