Entanglement convertibility by sweeping through the quantum phases of the alternating bonds $XXZ$ chain

TL;DR

This paper investigates the entanglement structure and topological properties of the ground state in an alternating bond XXZ spin chain, revealing how entanglement convertibility and edge states characterize different quantum phases.

Contribution

It introduces a detailed analysis of entanglement convertibility and edge state correlations to distinguish topological and non-topological phases in the XXZ model.

Findings

Entanglement convertibility is limited within the topological Haldane dimer phase at small scales.

The entanglement spectrum shows a large susceptibility in the topological phase.

Local responses can distinguish topological phases despite their non-local order.

Abstract

We study the entanglement structure and the topological edge states of the ground state of the spin-1/2 XXZ model with bond alternation. We employ parity-density matrix renormalization group with periodic boundary conditions. The finite-size scaling of R\'enyi entropies $S_2$ and $S_\infty$ are used to construct the phase diagram of the system. The phase diagram displays three possible phases: Haldane type (an example of symmetry protected topological ordered phases), Classical Dimer and N\'eel phases, the latter bounded by two continuous quantum phase transitions. The entanglement and non-locality in the ground state are studied and quantified by the entanglement convertibility. We found that, at small spatial scales, the ground state is not convertible within the topological Haldane dimer phase. The phenomenology we observe can be described in terms of correlations between edge states. We found that the entanglement spectrum also exhibits a distinctive response in the topological phase: the effective rank of the reduced density matrix displays a specifically large "susceptibility" in the topological phase. These findings support the idea that although the topological order in the ground state cannot be detected by local inspection, the ground state response at local scale can tell the topological phases apart from the non-topological phases.