Vibronic excitation dynamics in orbitally degenerate correlated electron system

Nasu, Joji; Ishihara, Sumio

doi:10.1103/physrevb.88.205110

Cited by 17 publications

(11 citation statements)

References 52 publications

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“…The collective excitations are calculated using the generalized spin-wave method proposed in Ref. [39], which is equivalent to the methods in Refs. [40][41][42][43][44][45].…”

Section: Methodsmentioning

confidence: 99%

Phase diagram and collective excitations in an excitonic insulator from an orbital physics viewpoint

et al. 2016

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An excitonic-insulating system is studied from a viewpoint of the orbital physics in strongly correlated electron systems. An effective model Hamiltonian for low-energy electronic states is derived from the two-orbital Hubbard model with a finite energy difference corresponding to the crystalline-field splitting. The effective model is represented by the spin operators and the pseudo-spin operators for the spin-state degrees of freedom. The ground state phase diagram is analyzed by the mean-field approximation. In addition to the low-spin state and high-spin state phases, two kinds of the excitonic-insulating phases emerge as a consequence of the competition between the crystalline-field effect and the Hund coupling. Transitions to the excitonic phases are classified to an Ising-like transition resulted from a spontaneous breaking of the Z 2 symmetry. Magnetic structures in the two excitonic-insulating phases are different from each other; an antiferromagnetic order and a spin nematic order. Collective excitations in each phase are examined using the generalized spin-wave approximation. Characteristics in the Goldstone modes in the excitonic-insulating phases are studied through the calculations of the dynamical correlation functions for the spins and pseudo-spin operators. Both the transverse and longitudinal spin excitation modes are active in the two excitonic-insulating phases in contrast to the low-spin state and high-spin state phases. Relationships of the present results to the perovskite cobalt oxides are discussed.

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“…The collective excitations are calculated using the generalized spin-wave method proposed in Ref. [39], which is equivalent to the methods in Refs. [40][41][42][43][44][45].…”

Section: Methodsmentioning

confidence: 99%

Phase diagram and collective excitations in an excitonic insulator from an orbital physics viewpoint

et al. 2016

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“…Fig. 5(b) of [20]. Since the Jahn-Teller coupling is inherently strong in KCuF 3 we believe this scenario explains the effective disappearance of the orbiton dispersion in this compound.…”

Section: Resultsmentioning

confidence: 80%

“…As discussed in Ref. [20], the latter effect, which should be present in any Jahn-Teller active system, can lead to a strong dressing of the orbitons with local vibrational modes and may cause a complete smearing out of the orbiton dispersion, cf. Fig.…”

Section: Resultsmentioning

confidence: 90%

“…Apart from the cooperative, global Jahn-Teller effect and ordering, the local Jahn-Teller effect, i.e. the Jahn-Teller coupling between the orbital degrees of freedom and the local lattice vibrations is of prime importance [20,37]. As discussed in Ref.…”

Section: Resultsmentioning

confidence: 97%

“…As already discussed, the OO itself is mostly driven by the JT mechanism. Since the JT Hamiltonian has an identical form to the orbital part of the superexchange one [9,[18][19][20], one could imagine that it should also lead to the onset of the orbiton dispersion, that is identical to the one predicted by the orbital part of the superexchange model, albeit at a much larger energy scale ∝ T OO ∼ 800K…”

Section: Introductionmentioning

confidence: 99%

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Unraveling the orbital physics in a canonical orbital system KCuF$_3$

Li,

Xu,

Garcia-Fernandez

et al. 2020

Preprint

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We study the collective spin and orbital excitations in the canonical orbital system KCuF3. Using the Cu L3-edge resonant inelastic X-ray scattering we show that the non-dispersive high-energy peaks result from the Cu 2+ dd orbital excitations. These high-energy modes show good agreement with the ab-initio quantum chemistry calculation based on a single cluster, indicating that the dd excitations are highly localized. At the same time, the low-energy excitations present clear dispersion. They match extremely well with the two-spinon continuum following the comparison with Mueller Ansatz calculations. The localized dd excitations and the observation of the strongly dispersive magnetic excitations suggest that orbiton dispersion is below the resolution detection limit. Our results can reconcile with the strong local Jahn-Teller effect in KCuF3, which predominantly drives orbital ordering.

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Resonant X-ray Scattering and Orbital Degree of Freedom in Correlated Electron Systems

Ishihara

2016

Resonant X-Ray Scattering in Correlated Systems

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Vibronic excitation dynamics in orbitally degenerate correlated electron system

Cited by 17 publications

References 52 publications

Phase diagram and collective excitations in an excitonic insulator from an orbital physics viewpoint

Phase diagram and collective excitations in an excitonic insulator from an orbital physics viewpoint

Unraveling the orbital physics in a canonical orbital system KCuF$_3$

Resonant X-ray Scattering and Orbital Degree of Freedom in Correlated Electron Systems

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