4,808 research outputs found
A brief review of recent advances on the Mott transition: unconventional transport, spectral weight transfers, and critical behaviour
Strongly correlated metals close to the Mott transition display unusual
transport regimes, together with large spectral weight transfers in optics and
photoemission. We briefly review the theoretical understanding of these
effects, based on the dynamical mean-field theory, and emphasize the key role
played by the two energy scales associated with quasiparticle coherence scale
and with the Mott gap. Recent experimental results on two-dimensional organic
compounds and transition metal oxides are considered in this perspective. The
liquid-gas critical behaviour at the Mott critical endpoint is also discussed.
Transport calculations using the numerical renormalization group are presented.Comment: Review article. 9 pages, 5 figures. Proceedings of the Vth
International Conference on Crystalline Organic Metals, Superconductors and
Magnets (ISCOM 2003
Deconfinement transition and Luttinger to Fermi Liquid crossover in quasi one-dimensional systems
We investigate a system of one dimensional Hubbard chains of interacting
fermions coupled by inter-chain hopping. Using a generalization of the
Dynamical Mean Field Theory we study the deconfinement transition from a Mott
insulator to a metal and the crossover between Luttinger and Fermi liquid
phases. One-particle properties, local spin response and inter-chain optical
conductivity are calculated. Possible applications to organic conductors are
discussed.Comment: 5 page
Electronic correlations, magnetism and Hund's rule coupling in the ruthenium perovskites SrRuO and CaRuO
A comparative density functional plus dynamical mean field theory study of
the pseudocubic ruthenate materials CaRuO and SrRuO is presented. Phase
diagrams are determined for both materials as a function of Hubbard repulsion
and Hund's rule coupling . Metallic and insulating phases are found, as
are ferromagnetic and paramagnetic states. The locations of the relevant phase
boundaries are determined. Based on the computed phase diagrams, Mott-dominated
and Hund's dominated regimes of strong correlation are distinguished.
Comparison of calculated properties to experiments indicates that the actual
materials are in the Hund's coupling dominated region of the phase diagram so
can be characterized as Hund's metals, in common with other members of the
ruthenate family. Comparison of the phase diagrams for the two materials
reveals the role played by rotational and tilt (GdFeO-type) distortions of
the ideal perovskite structure. The presence of magnetism in SrRuO and its
absence in CaRuO despite the larger mass and larger tilt/rotational
distortion amplitude of CaRuO can be understood in terms of density of
states effects in the presence of strong Hund's coupling. Comparison of the
calculated low- properties of CaRuO to those of SrRuO provides
insight into the effects of magnetic order on the properties of a Hund's metal.
The study provides a simultaneous description of magnetism and correlations and
explicates the roles played by band theory and Hubbard and Hund's interactions
Spin wave contribution to the nuclear spin-lattice relaxation in triplet superconductors
We discuss collective spin wave excitations in triplet superconductors with
an easy axis anisotropy for the order parameter. Using a microscopic model for
interacting electrons we estimate the frequency of such excitations in
Bechgaard salts and ruthenate superconductors to be one and twenty GHz
respectively. We introduce an effective bosonic model to describe spin-wave
excitations and calculate their contribution to the nuclear spin lattice
relaxation rate. We find that in the experimentally relevant regime of
temperatures, this mechanism leads to the power law scaling of 1/T_1 with
temperature. For two and three dimensional systems the scaling exponents are
three and five respectively. We discuss experimental manifestations of the spin
wave mechanism of the nuclear spin lattice relaxation.Comment: 4 pages, 2 figure
Effect of Kondo resonance on optical third harmonic generation
We use the method of dynamical mean field thoery, to study the effect of
Kondo resonance on optical third harmonic generation (THG) spectra of strongly
correlated systems across the metal-insulator transition. We find that THG
signals are proportional to the quasiparticle weight of the Kondo peak, and
are precursors of Mott-Hubbard gap formation.Comment: ICM 2006 (kyoto) proceedin
A worldwide gathering and comparative analysis of Camarena-Chevalier type 714, II-IV tales
Primeira parte de um artigo sobre um conto-tipo que, não estando registado nos
catálogos internacionais, foi classificado no Catálogo de Camarena e Chevalier com
o nº [714]. É a história duma mulher abandonada numa ilha desabitada e que é
forçada a tornar-se mulher de um grande símio. Quando vem a ser socorrida pela
tripulação dum navio que aporta à ilha, o símio mata o filho à vista da mãe. Os
relatos mais recuados desta história remetem-na para os “Anais de Castanheda”.
Embora a narrativa esteja ausente da História de Fernão Lopes Castanheda, aparece
na tradição oral portuguesa. Nesta primeira parte do artigo dá-se conta da tradição
escrita (e oral) desta narrativa também em Espanha, Itália, França e Inglaterra. 714, II-IV tale
Equation of motion approach to the Hubbard model in infinite dimensions
We consider the Hubbard model on the infinite-dimensional Bethe lattice and
construct a systematic series of self-consistent approximations to the
one-particle Green's function, . The first
equations of motion are exactly fullfilled by and the
'th equation of motion is decoupled following a simple set of decoupling
rules. corresponds to the Hubbard-III approximation. We
present analytic and numerical results for the Mott-Hubbard transition at half
filling for .Comment: 10pager, REVTEX, 8-figures not available in postscript, manuscript
may be understood without figure
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