Cluster Dynamical Mean Field Analysis of the Mott Transition

Parcollet, Olivier; Biroli, Giulio; Kotliar, Gabriel

doi:10.1103/physrevlett.92.226402

Cited by 179 publications

(221 citation statements)

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“…Note that the critical interaction strength U c is much larger than the crossover strength of U found for the unfrustrated square lattice [14]. As is the case for the triangular-lattice Hubbard model [11], the double occupancy D occ. increases in the metallic phase (U < U c ) as T decreases, while it is almost independent of T in the insulating phase (U > U c ).…”

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confidence: 81%

“…The dynamical mean field theory (DMFT) [10] has given substantial theoretical progress in the field of the Mott transition but it does not incorporate spatially extended correlations. In order to treat both strong correlations and frustration, we use CDMFT, a cluster extension of DMFT, which has been successfully applied to frustrated systems such as the Hubbard model on the triangular lattice [11].…”

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confidence: 99%

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Mott Transition in Kagomé Lattice Hubbard Model

2006

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We investigate the Mott transition in the Kagomé lattice Hubbard model using a cluster extension of dynamical mean field theory. The calculation of the double occupancy, the density of states, the static and dynamical spin correlation functions demonstrates that the system undergoes the firstorder Mott transition at the Hubbard interaction U/W ∼ 1.4 (W :bandwidth). In the metallic phase close to the Mott transition, we find the strong renormalization of three distinct bands, giving rise to the formation of heavy quasiparticles with strong frustration. It is elucidated that the quasiparticle states exhibit anomalous behavior in the temperature-dependent spin correlation functions. The Kagomé lattice (Fig. 1) is another prototype of frustrated systems, which may be regarded as a twodimensional analog of the pyrochlore lattice. It is suggested that a correlated electron system on the Kagomé lattice can be an effective model of Na x CoO 2 · yH 2 O by properly considering anisotropic hopping matrix elements in the cobalt 3d orbitals [6]. The issue of electron correlations for the Kagomé lattice was addressed recently by using the FLEX approximation [7] and QMC method [8]. These studies focused on electron correlations in the metallic regime, and the nature of the Mott transition has not been clarified yet. Therefore, it is desirable to investigate the Kagomé lattice electron system with particular emphasis on the Mott transition under the influence of strong frustration.In this paper, we study the Mott transition of correlated electrons on the Kagomé lattice by means of the cellular dynamical mean field theory (CDFMT) [9]. It is shown that the metallic phase persists up to fairly large Coulomb interactions due to the frustrated lattice structure. This gives rise to the strong renormalization of three distinct bands, resulting in the multi-band quasiparticles with strong frustration near the Mott transition. In particular, we find that the quasiparticles exhibit anomalous behavior in spin correlation functions, which characterizes strong frustration in the metallic phase.We consider the standard Hubbard model with nearest-neighbor hopping on the Kagomé lattice,with n iσ = c † iσ c iσ , where c † iσ (c jσ ) creates (annihilates) an electron with spin σ at site i. We use the band width W = 6t as the energy unit. To study the Mott transition in the Kagomé lattice system, we need an efficient theoretical tool to treat both of strong correlations and geometrical frustration. The dynamical mean field theory (DMFT) [10] has given substantial theoretical progress in the field of the Mott transition but it does not incorporate spatially extended correlations. In order to treat both strong correlations and frustration, we use CDMFT, a cluster extension of DMFT, which has been successfully applied to frustrated systems such as the Hubbard model on the triangular lattice [11].In CDMFT, the original lattice is regarded as a superlattice consisting of clusters, which is then mapped onto an effective cluster model via a standard DMF...

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Mott Transition in Kagomé Lattice Hubbard Model

2006

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“…Variational calculations based on the dimer model plus additional exchange terms reveal a transition between dSC and an AF insulator [11]. Cellular Dynamical Mean Field Theory (CDMFT) [12] has also been used to reveal the Mott transition in that case, without treating the broken symmetry phases.…”

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Antiferromagnetism and Superconductivity in Layered Organic Conductors: Variational Cluster Approach

Sahebsara

Sénéchal

2006

Phys. Rev. Lett.

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The κ-(ET)2X layered conductors (where ET stands for BEDT-TTF) are studied within the dimer model as a function of the diagonal hopping t ′ and Hubbard repulsion U . Antiferromagnetism and d-wave superconductivity are investigated at zero temperature using variational cluster perturbation theory (V-CPT). For large U , Néel antiferromagnetism exists for t ′ < t ′ c2 , with t ′ c2 ∼ 0.9. For fixed t ′ , as U is decreased (or pressure increased), a d x 2 −y 2 superconducting phase appears. When U is decreased further, the a dxy order takes over. There is a critical value of t ′ c1 ∼ 0.8 of t ′ beyond which the AF and dSC phases are separated by Mott disordered phase.The proximity of antiferromagnetism (AF) and d-wave superconductivity (dSC) is a central and universal feature of high-temperature superconductors, and leads naturally to the hypothesis that the mechanisms behind the two phases are intimately related. This proximity is also observed in the layered organic conductor κ-(ET) 2 Cu-[N(CN) 2 ]Cl, an antiferromagnet that transits to a superconducting phase upon applying pressure[1] (here ET stands for BEDT-TTF). Other compounds of the same family, κ-(ET) 2 Cu(NCS) 2 and κ-(ET) 2 Cu[N(CN) 2 ]Br, are superconductors with a critical temperature near 10K at ambient pressure. However, another member of this family, κ-(ET) 2 Cu 2 (CN) 3 , displays no sign of AF order, but becomes superconducting upon applying pressure [2,3]. The character of the superconductivity in these compounds is still controversial. While many experiments indicate that the SC gap has nodes (presumably d-wave), others are interpreted as favoring a nodeless gap. The literature on the subject is rich, and we refer to a recent review article[4] for references.The interplay of AF and dSC orders, common to both high-T c and κ-ET materials, cannot be fortuitous and must be a robust feature that can be captured in a simple model of these strongly correlated systems. κ-ET compounds consist of orthogonally aligned ET dimers that form conducting layers sandwiched between insulating polymerized anion layers. The simplest theoretical description of these complex compounds is the so-called dimer Hubbard model [5,6] (Fig. 1A) in which a single bonding orbital is considered on each dimer, occupied by one electron on average, with the Hamiltonianwhere c rσ (c † rσ ) creates an electron (hole) at dimer site r on a square lattice with spin projection σ, and n rσ =c † rσ c rσ is the hole number operator. rr ′ ([rr ′ ]) indicates nearest-(next-nearest)-neighbor bonds. As the ratio t ′ /t grows from 0 towards 1, Néel AF is increasingly

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“…There is compelling experimental evidence that the quasiparticle coherence scale then has a strong variation as the momentum k is varied along the Fermi surface, leading to the formation of "cold spots" and "hot regions". Such effects have been found in recent studies using cluster extensions of the DMFT framework ( [119], see also [39,120]). …”

Section: The Frontier: K-dependent Coherence Scale Cold and Hot Spotsmentioning

confidence: 72%

Strongly Correlated Electron Materials: Dynamical Mean-Field Theory and Electronic Structure

Georges¹

2004

AIP Conference Proceedings

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Abstract. These are introductory lectures to some aspects of the physics of strongly correlated electron systems. I first explain the main reasons for strong correlations in several classes of materials. The basic principles of dynamical mean-field theory (DMFT) are then briefly reviewed. I emphasize the formal analogies with classical mean-field theory and density functional theory, through the construction of free-energy functionals of a local observable. I review the application of DMFT to the Mott transition, and compare to recent spectroscopy and transport experiments. The key role of the quasiparticle coherence scale, and of transfers of spectral weight between low-and intermediate or high energies is emphasized. Above this scale, correlated metals enter an incoherent regime with unusual transport properties. The recent combinations of DMFT with electronic structure methods are also discussed, and illustrated by some applications to transition metal oxides and f-electron materials.

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Cluster Dynamical Mean Field Analysis of the Mott Transition

Cited by 179 publications

References 26 publications

Mott Transition in Kagomé Lattice Hubbard Model

Mott Transition in Kagomé Lattice Hubbard Model

Antiferromagnetism and Superconductivity in Layered Organic Conductors: Variational Cluster Approach

Strongly Correlated Electron Materials: Dynamical Mean-Field Theory and Electronic Structure

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