Evolution of Spin-Orbital Entanglement with Increasing Ising Spin-Orbit Coupling

TL;DR

This paper investigates how spin-orbital entanglement in quantum materials evolves with increasing Ising spin-orbit coupling, revealing both amplification and potential disentanglement effects in a 1D model.

Contribution

It demonstrates that strong spin-orbit coupling can enhance entanglement but also lead to nearly classical states, providing new insights into quantum entanglement behavior in spin-orbital systems.

Findings

Entanglement is amplified by strong spin-orbit coupling.

Almost classical disentangled states can occur.

Entanglement can disappear at higher spin-orbit coupling values.

Abstract

Several realistic spin-orbital models for transition metal oxides go beyond the classical expectations and could be understood only by employing the quantum entanglement. Experiments on these materials confirm that spin-orbital entanglement has measurable consequences. Here, we capture the essential features of spin-orbital entanglement in complex quantum matter utilizing 1D spin-orbital model which accommodates SU(2)xSU(2) symmetric Kugel-Khomskii superexchange as well as the Ising on-site spin-orbit coupling. Building on the results obtained for full and effective models in the regime of strong spin-orbit coupling, we address the question whether the entanglement found on superexchange bonds always increases when the Ising spin-orbit coupling is added. We show that (i) quantum entanglement is amplified by strong spin-orbit coupling and, surprisingly, (ii) almost classical disentangled states are possible. We complete the latter case by analyzing how the entanglement existing for intermediate values of spin-orbit coupling can disappear for higher values of this coupling.