Orbital-selective Mott transitions in two-band Hubbard models

Blümer, N.; Knecht, C.; Požgajčić, Krunoslav; Dongen, P. G. J. van

doi:10.1016/j.jmmm.2006.10.525

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…The QMC phase diagram, presented here, is in qualitative agreement with the results of Rüegg et al , 34 which were obtained based on variational methods. As a remark we add that, since, in the OSMP at half filling, the wide band is in a non-Fermi-liquid state, 36 by continuity one also expects a non-Fermi-liquid state in the OSMP at low doping. Signatures of such a non-Fermi-liquid state away from half filling will indeed be found and discussed below.…”

Section: Phase Diagrammentioning

confidence: 85%

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Orbital-selective Mott transitions in a doped two-band Hubbard model

2009

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We extend previous studies on orbital-selective Mott transitions in the paramagnetic state of the half-filled degenerate two-band Hubbard model to the general doped case, using a high-precision quantum Monte Carlo dynamical mean-field theory solver. For sufficiently strong interactions, orbital-selective Mott transitions as a function of total band filling are clearly visible in the band-specific fillings, quasiparticle weights, double occupancies, and spectra. The results are contrasted with those of single-band models for similar correlation strengths.

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Section: Phase Diagrammentioning

confidence: 85%

“…In this paper, we extend high-precision 35 quantum Monte Carlo (QMC) calculations 28,30,36 within DMFT for two-band model (1) to general doping levels. Of central interest is the phase diagram, which is derived from orbital-dependent fillings, double occupancies, and quasiparticle weights.…”

Section: Introductionmentioning

confidence: 99%

Orbital-selective Mott transitions in a doped two-band Hubbard model

2009

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Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
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We present a strongly correlated mean-field theory of the ionic Hubbard model on the triangular lattice with alternating stripes of site energy using Barnes-Coleman slave bosons. We study the paramagnetic phases of this theory at three quarters filling, where it is a model of Na 0.5 CoO 2 , Rb 0.5 CoO 2 , and K 0.5 CoO 2 . This theory has two bands of fermionic quasiparticles: one of which is filled or nearly filled and hence weakly correlated; the other is half-filled or nearly half-filled and hence strongly correlated. Further results depend strongly on the sign of the hopping integral t. The light band is always filled for t Ͼ 0, but only becomes filled for ͉⌬ / t͉ Ն 1.5 for t Ͻ 0, where ⌬ is the difference in the site energies of the two sublattices. A metal-charge transfer insulator transition occurs at ͉⌬ / t͉ = 5.0 for t Ͼ 0 and ͉⌬ / t͉ = 8.0 for t Ͻ 0. In the charge transfer insulator complete charge disproportionation occurs: one sublattice is filled and the other is half-filled. We compare our results with exact diagonalization calculations and experiments on Na 0.5 CoO 2 and discuss the relevance of our results to Rb 0.5 CoO 2 and K 0.5 CoO 2 . We propose a resolution of seemingly contradictory experimental results on Na 0.5 CoO 2 . Many experiments suggest that there is a charge gap, yet quantum oscillations are observed suggesting the existence of quasiparticle states at arbitrarily low excitation energies. We argue that the heavy band is gapped while the light band, which contains less than one charge carrier per 100 unit cells, remains ungapped.

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Determinant Quantum Monte Carlo Study of the Orbitally Selective Mott Transition

2009

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We study the conductivity, density of states, and magnetic correlations of a two dimensional, two band fermion Hubbard model using determinant Quantum Monte Carlo (DQMC) simulations. We show that an orbitally selective Mott transition (OSMT) occurs in which the more weakly interacting band can be metallic despite complete localization of the strongly interacting band. The DQMC method allows us to test the validity of the use of a momentum independent self-energy which has been a central approximation in previous OSMT studies. In addition, we show that long range antiferromagnetic order (LRAFO) is established in the insulating phase, similar to the single band, square lattice Hubbard Hamiltonian. Because the critical interaction strengths for the onset of insulating behavior are much less than the bandwidth of the itinerant orbital, we suggest that the development of LRAFO plays a key role in the transitions. PACS numbers:Introduction: The problem of a strongly correlated band put in contact with a more weakly interacting one is of long-standing interest. In the case of the periodic Anderson model (PAM), for example, one orbital is completely free of interactions, while a second orbital is at the opposite extreme: it has no hopping from site-to-site (zero bandwidth) and instead has only an on-site hybridization V with the uncorrelated band. A competition between on-site singlet formation between electrons in the two different orbitals and RKKY mediated antiferromagnetic (AF) order occurs as a function of V , and a resonance in the density of states at the Fermi surface is present at the transition between these two regimes.Recently there have been a number of studies, 1,2,3,5 mainly within dynamical mean field theory (DMFT) 6 , of the general question whether two different bands can exist with one metallic and the other insulating, the socalled 'orbitally selective Mott transition' (OSMT). Alternate methods of treating the correlations of the impurity problem arising within DMFT, ranging from iterated perturbation theory 1 to Quantum Monte Carlo (QMC) 1,2 and exact diagonalization 3,4 yield different results. The form of the interband coupling and, specifically, whether the Hund's rule term is treated in an SU(2) symmetric way or only an Ising term is retained, was also thought to affect the results. By now it is established that, within DMFT and using the most accurate impurity solvers, an OSMT is possible. As might be expected, the narrow band becomes insulating first, as correlations increase, followed by the wide band. Attention has also focussed on the nature of the transitions which are, in general, believed to be first order.The most well controlled theoretical work on the OSMT has been formulated within the framework of model Hamiltonians (multiband Hubbard models) whose simplicity allows for detailed and precise numerical studies. However, similar issues have also been addressed using a combination of electronic structure and manybody methods to describe real materials. The Cerium

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Orbital-selective Mott transitions in two-band Hubbard models

Cited by 4 publications

References 10 publications

Orbital-selective Mott transitions in a doped two-band Hubbard model

Orbital-selective Mott transitions in a doped two-band Hubbard model

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
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Determinant Quantum Monte Carlo Study of the Orbitally Selective Mott Transition

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Orbital-selective Mott transitions in two-band Hubbard models

Cited by 4 publications

References 10 publications

Orbital-selective Mott transitions in a doped two-band Hubbard model

Orbital-selective Mott transitions in a doped two-band Hubbard model

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5Powell1, Merino2, McKenzie3 2009Phys. Rev. B9020View full textAdd to dashboardCite

Determinant Quantum Monte Carlo Study of the Orbitally Selective Mott Transition

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Product

Resources

About

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
View full text Add to dashboard Cite