1,721,059 research outputs found
Cellular-dynamical mean-field theory of the competition between antiferromagnetism and d-wave superconductivity in the two-dimensional Hubbard model
No full textCellular dynamical mean field theory is used to study the competition of antiferromagnetism and d-wave superconductivity at zero-temperature in the two-dimensional Hubbard model. The outcome strongly depends on the value of the interaction. At strong coupling (U >= 8t) a first-order transition takes place as a function of doping between pure antiferromagnet and pure superconductor. At weak-coupling instead (U <= 8t) the groundstate has both antiferromagnetic and d-wave long-range order, and the system smoothly evolves from one phase to the other. The first-order transition at large interactions is accompanied by a phase separation. (c) 2006 Elsevier B.V. All rights reserved. RI Capone, Massimo/A-7762-200
Competition between d-wave superconductivity and antiferromagnetism in the two-dimensional Hubbard model
No full textWe study the competition of antiferromagnetism and d-wave superconductivity at zero temperature in the two-dimensional Hubbard model using cellular dynamical mean-field theory for a 2x2 plaquette, and solve the associated cluster impurity model at zero temperature by means of exact diagonalization. The interplay between the two phases depends strongly on the strength of the correlation. At strong coupling (U greater than or similar to 8t) the two phases do not mix, and a first-order transition takes place as a function of doping between two pure phases. At weak coupling (U less than or similar to 8t) the two order parameters coexist within the same solution in a range of doping and the system smoothly evolves from the antiferromagnet to the superconductor. When the transition between the superconducting and the antiferromagetic phases is of the first-order, it is accompanied by a phase separation. RI Capone, Massimo/A-7762-200
Dynamical breakup of the Fermi surface in a doped Mott insulator
No full textThe evolution from an anomalous metallic phase to a Mott insulator within the two-dimensional Hubbard model is investigated by means of the cellular dynamical mean-field theory. We show that approaching the density-driven Mott metal-insulator transition the Fermi surface is strongly renormalized and the quasiparticle description breaks down in a very anisotropic fashion. Regions where the quasiparticles are strongly scattered (hot spots) and regions where the scattering rate is relatively weak (cold spot) form irrespective of whether the parent insulator has antiferromagnetic long-range order, while their location is not universal and is determined by the interplay of the renormalization of the scattering rate and the Fermi surface shape. RI Parcollet, Olivier/C-2340-2008; Capone, Massimo/A-7762-200
SCALING THEORY OF THE HALL-COEFFICIENT NEAR THE METAL-INSULATOR-TRANSITION, A RENORMALIZATION-GROUP APPROACH
No full textCorrelation-driven electronic multiferroicity in TMTTF2-X organic crystals
Full text linkUsing a combination of density functional theory and dynamical mean field theory we show that electric polarization and magnetism are strongly intertwined in TMTTF2-X (X=PF6, AsF6, and SbF6) organic crystals. Electronic correlations induce a charge-ordered state which, combined with the molecular dimerization, gives rise to a finite electronic polarization and to a ferroelectric state. The value of the electronic polarization is enhanced by the onset of antiferromagnetism showing a sizable magnetoelectric effect which predicts the multiferroic behavior of TMTTF2-X compounds
Fermi liquid theory of interacting disordered systems and the scaling theory of the metal-insulator transition
No full textMulti-patch model for transport properties of cuprate superconductors
No full textA number of normal state transport properties of cuprate superconductors are analyzed in detail using the Boltzmann equation. The momentum dependence of the electronic structure and the strong momentum anisotropy of the electronic scattering are included in a phenomenological way via a multi-patch model. The Brillouin zone and the Fermi surface are divided in regions where scattering between the electrons is strong and the Fermi velocity is low (hot patches) and in regions where the scattering is weak and the Fermi velocity is large (cold patches). We present several motivations for this phenomenology starting from various microscopic approaches. A solution of the Boltzmann equation in the case of N patches is obtained and an expression for the distribution function away from equilibrium is given. Within this framework, and limiting our analysis to the two patches case, the temperature dependence of resistivity, thermoelectric power, Hall angle, magnetoresistance and thermal Hall conductivity are studied in a systematic way analyzing the role of the patch geometry and the temperature dependence of the scattering rates. In the case of Bi-based cuprates, using ARPES data for the electronic structure, and assuming an inter-patch scattering between hot and cold states with a linear temperature dependence, a reasonable agreement with the available experiments is obtained
Nodal-antinodal dichotomy and the two gaps of a superconducting doped Mott insulator
No full textWe study the superconducting state of the hole-doped two-dimensional Hubbard model using cellular dynamical mean-field theory, with the Lanczos method as impurity solver. In the underdoped regime, we find a natural decomposition of the one-particle (photoemission) energy gap into two components. The gap in the nodal regions, stemming from the anomalous self-energy, decreases with decreasing doping. The antinodal gap has an additional contribution from the normal component of the self-energy, inherited from the normal-state pseudogap, and it increases as the Mott insulating phase is approached. RI Parcollet, Olivier/C-2340-2008; Capone, Massimo/A-7762-2008; Georges, Antoine/H-4855-201
Approach to a stationary state in a driven Hubbard model coupled to a thermostat
No full textWe investigate the dynamics of the Hubbard model in a static electric field in order to identify the conditions necessary to reach a nonequilibrium stationary state. We show that, for a generic electric field, the convergence to a stationary state requires coupling to a thermostatting bath that absorbs the work done by the external field. Following the real-time dynamics of the system, we show that a nonequilibrium stationary state is reached for essentially any value of the coupling to the bath. We characterize the properties of such nonequilibrium stationary states by studying suitable physical observables, pointing out the existence of an analog of the Pomeranchuk effect as a function of the electric field. We map out a phase diagram in terms of dissipation and electric field strengths and identify the dissipation values at which the steady current is largest for a given field. RI Capone, Massimo/A-7762-2008; Amaricci, Adriano/H-4183-201
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