How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator
| Authors | |
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| Year of publication | 2020 |
| Type | Article in Periodical |
| Magazine / Source | Physical Review Research |
| MU Faculty or unit | |
| Citation | |
| Web | https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.013353 |
| Doi | http://dx.doi.org/10.1103/PhysRevResearch.2.013353 |
| Keywords | Entanglement entropy; Orbital order; Spin-orbit coupling; Exact diagonalization |
| Description | The concept of the entanglement between spin and orbital degrees of freedom plays a crucial role in our understanding of various phases and exotic ground states in a broad class of materials, including orbitally ordered materials and spin liquids. We investigate how the spin-orbital entanglement in a Mott insulator depends on the value of the spin-orbit coupling of the relativistic origin. To this end, we numerically diagonalize a one-dimensional spin-orbital model with Kugel-Khomskii exchange interactions between spins and orbitals on different sites supplemented by the on-site spin-orbit coupling. In the regime of small spin-orbit coupling with regard to the spin-orbital exchange, the ground state to a large extent resembles the one obtained in the limit of vanishing spin-orbit coupling. On the other hand, for large spin-orbit coupling the ground state can, depending on the model parameters, either still show negligible spin-orbital entanglement or evolve to a highly spin-orbitally-entangled phase with completely distinct properties that are described by an effective XXZ model. The presented results suggest that (i) the spin-orbital entanglement may be induced by large on-site spin-orbit coupling, as found in the 5d transition metal oxides, such as the iridates; (ii) for Mott insulators with weak spin-orbit coupling of Ising type, such as, e.g., the alkali hyperoxides, the effects of the spin-orbit coupling on the ground state can, in the first order of perturbation theory, be neglected. |
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