Orbital-selective Mott transitions in a doped two-band Hubbard model with crystal field splitting

Jakobi, Eberhard; Blümer, N.; Dongen, Peter van

doi:10.1103/physrevb.87.205135

Cited by 24 publications

(22 citation statements)

References 49 publications

(62 reference statements)

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“…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.…”

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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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Coulomb Correlations Intertwined with Spin and Orbital Excitations in LaCoO3

et al. 2017

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“…Finally, we would emphasize that the difference between this mechanism of OSMT and previous studies [17][18][19] of the OSMT in doped multi-band Hubbard models. In their studies, the bands have different band width, so the effective Coulomb interaction strength is different for each band, which may lead to an OSMT.…”

Section: Resultsmentioning

confidence: 69%

Doping-driven orbital-selective Mott transition in multi-band Hubbard models with crystal field splitting

Wang

et al. 2016

Chinese Phys. B

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We have studied the doping-driven orbital-selective Mott transition in multi-band Hubbard models with equal band width in the presence of crystal field splitting. Crystal field splitting lifts one of the bands while leaving the others degenerate. We use single-site dynamical mean-field theory combined with continuous time quantum Monte Carlo impurity solver to calculate a phase diagram as a function of total electron filling N and crystal field splitting ∆. We find a large region of orbital-selective Mott phase in the phase diagram when the doping is large enough. Further analysis indicates that the large region of orbital-selective Mott phase is driven and stabilized by doping. Such models may account for the orbital-selective Mott transition in some doped realistic strongly correlated materials.

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“…the conventional Hubbard U , as well as of the higher order multipoles responsible of Hund's rules. For instance, the distinction between different orbitals brought about by the hopping integrals and the crystal field can be amplified by strong correlations, leading to pronounced orbital differentiation [7][8][9][10] , and eventually to the so-called orbital-selective Mott transitions (OSMT) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] where the orbitals with the narrowest bandwidth localise while the others are still itinerant. In addition, orbital degrees of freedom are expected to play an important role in determining which symmetry-broken phase is more likely to accompany the Mott transition when correlations grow at integer electron density.…”

Section: Introductionmentioning

confidence: 99%

Correlation-driven Lifshitz transition and orbital order in a two-band Hubbard model

et al. 2018

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We study by dynamical mean field theory the ground state of a quarter-filled Hubbard model of two bands with different bandwidths. At half-filling, this model is known to display an orbital selective Mott transition, with the narrower band undergoing Mott localisation while the wider one being still itinerant. At quarter-filling, the physical behaviour is different and to some extent reversed. The interaction generates an effective crystal field splitting, absent in the Hamiltonian, that tends to empty the narrower band in favour of the wider one, which also become more correlated than the former at odds with the orbital selective paradigm. Upon increasing the interaction, the depletion of the narrower band can continue till it empties completely and the system undergoes a topological Lifshitz transition into a half-filled single-band metal that eventually turns insulating. Alternatively, when the two bandwidths are not too different, a first order Mott transition intervenes before the Lifshitz's one. The properties of the Mott insulator are significantly affected by the interplay between spin and orbital degrees of freedom.

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Orbital-selective Mott transitions in a doped two-band Hubbard model with crystal field splitting

Cited by 24 publications

References 49 publications

Coulomb Correlations Intertwined with Spin and Orbital Excitations in LaCoO3

Coulomb Correlations Intertwined with Spin and Orbital Excitations in LaCoO3

Doping-driven orbital-selective Mott transition in multi-band Hubbard models with crystal field splitting

Correlation-driven Lifshitz transition and orbital order in a two-band Hubbard model

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