Thermodynamics of Symmetric Spin—Orbital Model: One- and Two-Dimensional Cases

Valiulin, V.E.; Mikheyenkov, A. V.; Кugel, K. I.; Барабанов, А. Ф.

doi:10.1134/s0021364019080125

Cited by 6 publications

(6 citation statements)

References 22 publications

(25 reference statements)

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“…It may come as a surprise that the concept of the spinorbital entanglement has so far been rigorously investigated only for the systems where the spins and orbitals at neighboring sites interact, as a result of the spin, orbital and spin-orbital (super)exchange processes in Mott insulators [27][28][29][52][53][54][55][56][57]. This case is physically relevant to all Mott insulators with negligible spin-orbit coupling of relativistic origin and with active orbital degrees of freedom [58]-e.g.…”

Section: Main Question(s) and Organization Of The Papermentioning

confidence: 99%

How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator

Gotfryd

Pärschke

Chaloupka

et al. 2020

Phys. Rev. Research

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The concept of the entanglement between spin and orbital degrees of freedom plays a crucial role in understanding 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 1D spin-orbital model with the '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 w.r.t. 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 can evolve to a highly spin-orbitally entangled phase with completely distinct properties that are described by an effective XXZ model. The presented results: (i) explain how the spin-orbital entanglement can be induced by large on-site spin-orbit coupling, as found in the 5d transition metal oxides, such as the iridates; (ii) suggest that for Mott insulators with weak spin-orbit coupling, such as e.g. the 3d or some of the 4d transition metal oxides, the effects of the spin-orbit coupling on the ground state can, in the first order of approximation, be neglected.

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Section: Main Question(s) and Organization Of The Papermentioning

confidence: 99%

How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator

Gotfryd

Pärschke

Chaloupka

et al. 2020

Phys. Rev. Research

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“…All these observations suggest that the entanglement is closely related to the tendency to the formation of specific order parameters. Indeed, since the maximum entanglement is observed at relatively large absolute values of the intersubsystem exchange K, we can relate the entanglement with the dominant role of the spin-pseudospin correlations [52]. At the same time, at large I and J, the spin-spin, pseudospin-pseudospin, or both correlation functions begin to dominate, thus destroying the entanglement between spin and pseudospin degrees of freedom.…”

Section: Discussionmentioning

confidence: 97%

The resistance of quantum entanglement to temperature in the Kugel-Khomskii model

Valiulin¹,

Mikheyenkov²,

Chtchelkatchev³

et al. 2022

Preprint

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The Kugel-Khomskii model with entangled spin and orbital degrees of freedom is a good testing ground for many important features in quantum information processing, such as robust gaps in the entanglement spectra. Here, we demonstrate that the entanglement can be also robust under effect of temperature within a wide range of parameters. It is shown, in particular, that the temperature dependence of entanglement often exhibits a nonmonotonic behavior. Namely, there turn out to be ranges of the model parameters, where entanglement is absent at zero temperature, but then, with an increase in temperature, it appears, passes through a maximum, and again vanishes. I. II. METHODSWe consider the Kugel-Khomskii model, see below Eqs. ( 1) and ( 2), with the conventional symmetric

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“…It requires neither checking the Bell's inequalities nor calculating the full density matrix. The corresponding two-site correlator can be determined either numerically, but with much less waste of resources, or even analytically [24].…”

Section: Interrelation Between Spin-pseudospin Correlation Functions ...mentioning

confidence: 99%

“…Unusual effects related to the spin-orbital correlations and the corresponding quantum entanglement are widely discussed in the current literature. In particular, the possibility of extraordinary spin-orbital quantum states and transitions between them was pointed out [21][22][23][24][25]. [26,27].…”

Section: Introductionmentioning

confidence: 99%

Quantum entanglement, local indicators, and the effect of external fields in the Kugel-Khomskii model

et al. 2020

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Using the exact diagonalization technique, we determine the energy spectrum and wave functions for finite chains described by the two-spin (Kugel-Khomskii) model with different types of intersubsystem exchange terms. The found solutions provide a possibility to address the problem of quantum entanglement inherent to this class of models. We put the main emphasis on the calculations of the concurrence treated as an adequate numerical measure of the entanglement. We also analyze the behavior of two-site correlation functions considered as a local indicator of entanglement. We construct the phase diagrams of the models involving the regions of nonzero entanglement. The pronounced effect of external fields, conjugated to both spin variables on the regions with entanglement, could both enhance and weaken the entanglement depending on the parameters of the models. I.

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Thermodynamics of Symmetric Spin—Orbital Model: One- and Two-Dimensional Cases

Cited by 6 publications

References 22 publications

How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator

How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator

The resistance of quantum entanglement to temperature in the Kugel-Khomskii model

Quantum entanglement, local indicators, and the effect of external fields in the Kugel-Khomskii model

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