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

• Main Authors: Dorota Gotfryd, Ekaterina Pärschke, Krzysztof Wohlfeld, Andrzej M. Oleś
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Condensed Matter
• Subjects: spin-orbital entanglement; spin-orbit coupling; product state; Mott insulator; antiferromagnet; ferromagnet
• Online Access: https://www.mdpi.com/2410-3896/5/3/53

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)⊗SU(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.