Multi-spin-state dynamics during insulator-metal crossover in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">LaCoO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>

Doi, A.; Fujioka, Jun; Fukuda, Tatsuo; Tsutsui, Satoshi; Okuyama, Daisuke; Taguchi, Y.; Arima, T.; Baron, Alfred Q. R.; Tokura, Y.

doi:10.1103/physrevb.90.081109

Cited by 24 publications

(14 citation statements)

References 22 publications

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“…This IS scenario has been popular until recently several theoretical studies 7,[16][17][18][19] revived the HS scenario in terms of the dynamically or statically mixed LS/HS state, which is corroborated by the result from x-ray absorption spectroscopy. 20 However, the latest inelastic x-ray scattering (IXS) and infrared spectroscopy experiments 21 indicates a complex spin-state disproportionation including all the LS, IS, and HS states. Much attention has been paid to an analogous cobaltite family, RBaCo 2 O 5.5 (R: Nd 22 , Gd 23 , Tb 24 , Dy 25 , Ho 26 and Y 27 ) with the nominal valence of Co ion being +3 because a long-range SSO has been found to occur in conjunction with a temperature-induced (TI) MIT.…”

Section: Introductionmentioning

confidence: 99%

Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x

et al. 2017

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The layered perovskite cobaltite RBaCo2O5.5 (R: rare-earth elements or Yttrium) exhibits an abrupt temperature-induced metal−insulator transition (MIT) and has been attributed to spinstate ordering (SSO) of Co 3+ ions. Here we investigated the hole doping member of PrBaCo2O5.5+x (0 ≤ x ≤ 0.24) with multiple techniques. The analysis on crystal and magnetic structures by electron and neutron diffraction confirm the SSO in the insulating phase of undoped PrBaCo2O5.5, which is melted by increasing the temperature across the MIT. In addition, we discovered that hole doping to PrBaCo2O5.5 also melts the SSO in conjunction with an insulator-metal transition. The experimental results from electron/neutron diffraction and soft x-ray absorption spectroscopy (XAS) all lead to the conclusion that hole-doping induced MIT occurs is in the same manner as the temperatureinduced MIT. Therefore, we propose a unified mechanism that dominates the temperature-and hole-doping-induced MITs in the PrBaCo2O5.5+x system. Specifically, this mechanism involves symmetry breaking coupled with a SSO in the paramagnetic phase. arXiv:1602.05687v2 [cond-mat.str-el]

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Section: Introductionmentioning

confidence: 99%

Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x

et al. 2017

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“…This scenario however led to an overestimated χ(T ) and motivated an intermediate-spin (IS) description. Band-structure calculations with Coulomb correlations included gave a strong boost for the IS picture [25][26][27][28][29][30]. In contrast, electron spin resonance [31], inelastic neutron scattering [32], and X-ray absorption spectroscopy (XAS) [33] showed that the lowest-energy excited state is a HS state which exhibits additional splitting owing to the spin-orbit interaction.…”

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confidence: 99%

Coulomb Correlations Intertwined with Spin and Orbital Excitations in LaCoO3

et al. 2017

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We carried out temperature-dependent (20 -550 K) measurements of resonant inelastic X-ray scattering on LaCoO3 to investigate the evolution of its electronic structure across the spin-state crossover. In combination with charge-transfer multiplet calculations, we accurately quantified the renomalized crystal-field excitation energies and spin-state populations. We show that the screening of the on-site Coulomb interaction of 3d electrons is orbital selective and coupled to the spin-state crossover in LaCoO3. The results establish that the gradual spin-state crossover is associated with a relative change of Coulomb energy versus bandwidth, leading to a Mott-type insulator-to-metal transition.PACS numbers: 75.30. Wx, 71.70.Ch, 78.70.En The orbital degree of freedom of an electron characterizes the shape of the electron cloud and its wave function. It plays an essential role in the physics of phase transitions in solids via the coupling of charge, spin and lattice degrees of freedom, even in the presence of strong Coulomb interactions, for example, as in Mott insulators. The spatial redistribution of the electron cloud as a function of an external parameter such as temperature often manifests as co-operative phenomena leading to a metal-insulator transition [1], orbital ordering [2, 3], nematic transition [4,5], spin-state transition [6-10], etc. These results in exotic properties like superconductivity, quantum criticality, colossal magnetoresistance, etc. As the Coulomb interaction is a key to Mott physics [11][12][13][14], one fundamental question in correlated electron systems with orbital degrees of freedom is: how do the Coulomb correlations change dynamically through the rearrangement of the electronic distribution? This is usually beyond the scope of even multi-orbital model Hamiltonians in which the Coulomb interaction parameters are considered inflexible. An important theoretical advance in this direction is the role of orbital selective screening [15]. The effective Coulomb interaction for t 2g electrons was shown to be significantly reduced due to efficient e g electron screening, providing an improved understanding of LaMO 3 (M = 3d transition metals from Ti to Cu) series of perovskite oxides. This concept of the screened on-site Coulomb interaction has been developed recently using the constrained random-phase-approximation technique [16][17][18].In this Letter, we exploited resonant inelastic X-ray scattering (RIXS) to investigate spin-orbital excitations in LaCoO 3 and to measure its spin-state populations and the renormalized crystal-field excitations across the spinstate transition. an ideal candidate to examine the role of orbital selective screening of Coulomb interactions as a function of temperature. We found that the spin-state crossover is driven by the thermal excitation of high-spin (HS) states and accompanied by the reduction in effective Coulomb energy and an increase of covalency, culminating in an effective Coulomb-energy-vs-bandwidth type insulator-tometal transition.arXiv:1708.044...

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“…The band gap arising due to site disproportionation offers a yet unexplored route to reconcile the otherwise metallic IS state with the experimentally observed low conductivity. [1][2][3] This holds in particular if the emerging FM domains are embedded in an insulating NM matrix. 25 Finally, we note that a similar electronic structure is obtained for all systems in the IS state throughout this work.…”

Section: Computational Detailsmentioning

confidence: 95%

“…The emerging band gap offers a yet unexplored route to reconcile the otherwise metallic IS state with the experimentally observed low conductivity during the thermally driven spin transition of bulk LCO. [1][2][3]…”

Section: Introductionmentioning

confidence: 99%

Competition of defect ordering and site disproportionation in strained LaCoO3 on SrTiO3 (001)

Geisler

2020

Phys. Rev. B

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The origin of the 3 × 1 reconstruction observed in epitaxial LaCoO3 films on SrTiO3(001) is assessed by using first-principles calculations including a Coulomb repulsion term. We compile a phase diagram as a function of the oxygen pressure, which shows that (3 × 1)-ordered oxygen vacancies (LaCoO2.67) are favored under commonly used growth conditions, while stoichiometric films emerge under oxygen-rich conditions. Growth of further reduced LaCoO2.5 brownmillerite films is impeded by phase separation. We report two competing ground-state candidates for stoichiometric films: a semimetallic phase with 3 × 1 low-spin/intermediatespin/intermediate-spin magnetic order and a semiconducting phase with intermediate-spin magnetic order. This demonstrates that tensile strain induces ferromagnetism even in the absence of oxygen vacancies. Both phases exhibit an intriguing (3 × 1)-reconstructed octahedral rotation pattern and accordingly modulated La-La distances. In particular, charge and bond disproportionation and concomitant orbital order of the t2g hole emerge at the Co sites that are also observed for unstrained bulk LaCoO3 in the intermediate-spin state and explain structural data obtained by x-ray diffraction at elevated temperature. Site disproportionation drives a metalto-semiconductor transition that reconciles the intermediate-spin state with the experimentally observed low conductivity during spin-state crossover without Jahn-Teller distortions.arXiv:2003.02317v1 [cond-mat.mtrl-sci]

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Multi-spin-state dynamics during insulator-metal crossover inLaCoO3

Cited by 24 publications

References 22 publications

Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x

Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x

Coulomb Correlations Intertwined with Spin and Orbital Excitations in LaCoO3

Competition of defect ordering and site disproportionation in strained LaCoO3 on SrTiO3 (001)

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