In: Physical Review B, 2014, vol. 90, no. 19, p. 195114
Using extended dynamical mean-field theory and its combination with the GW approximation, we compute the phase diagrams and local spectral functions of the single-band extended Hubbard model on the square and simple cubic lattices, considering long-range interactions up to the third nearest neighbors. The longer-range interactions shift the boundaries between the metallic, charge-ordered...
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In: Physical Review D, 2014, vol. 90, no. 6, p. 065008
We review the extended mean field theory (EMFT) approximation and apply it to complex, scalar φ4 theory on the lattice. We study the critical properties of the Bose condensation driven by a nonzero chemical potential μ at both zero and nonzero temperature and determine the (T,μ) phase diagram. The results are in very good agreement with recent Monte Carlo data for all parameter values...
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In: Physical Review B, 2014, vol. 90, no. 11, p. 115435
We propose an electron-phonon parametrization which is constructed to reproduce target geometry and harmonic frequencies taken from first principles calculations or experiment. With respect to standard electron-phonon models, it adds a “double-counting” correction, which takes into account the lattice deformation as the system is dressed by low-energy electron-phonon processes. We show the...
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In: Reviews of Modern Physics, 2014, vol. 86, no. 2, p. 779–837
The study of nonequilibrium phenomena in correlated lattice systems has developed into one of the most active and exciting branches of condensed matter physics. This research field provides rich new insights that could not be obtained from the study of equilibrium situations, and the theoretical understanding of the physics often requires the development of new concepts and methods. On the...
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In: Journal of Statistical Mechanics: Theory and Experiment, 2014, vol. 2014, no. 6, p. P06012
We explore two complementary modifications of the hybridization-expansion continuous-time Monte Carlo method, aiming at large multi-orbital quantum impurity problems. One idea is to compute the imaginary-time propagation using a matrix product state representation. We show that bond dimensions considerably smaller than the dimension of the Hilbert space are sufficient to obtain accurate results...
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In: Physical Review B, 2014, vol. 89, no. 24, p. 245104
We study the competition of Coulomb interaction and hybridization effects in the five-orbital Anderson impurity model by means of continuous time quantum Monte Carlo, exact diagonalization, and Hartree-Fock calculations. The dependence of the electronic excitation spectra and thermodynamic ground-state properties on the hybridization strength and the form of the Coulomb interaction is...
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In: Physical Review B, 2013, vol. 88, no. 23, p. 235110
We present a detailed calculation of the electronic structure of SrVO3 based on the GW+DMFT method. We show that a proper inclusion of the frequency-dependent Hubbard U and the nonlocal self-energy via the GW approximation, as well as a careful treatment of the Fermi level, are crucial for obtaining an accurate and coherent picture of the quasiparticle band structure and satellite features of...
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In: Physical Review D, 2013, vol. 88, no. 12, p. 125006
We apply the dynamical mean field theory (DMFT) approximation to the real, scalar φ4 quantum field theory. By comparing to lattice Monte Carlo calculations, perturbation theory and standard mean field theory, we test the quality of the approximation in two, three, four and five dimensions. The quantities considered in these tests are the critical coupling for the transition to the ordered phase...
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In: Physical Review B, 2013, vol. 88, no. 16, p. 165108
We study quenches of the interaction and electron-phonon coupling parameter in the Hubbard-Holstein model, using nonequilibrium dynamical mean field theory. The calculations are based on a generalized Lang-Firsov scheme for time-dependent interactions or externally driven phonons, and an approximate strong-coupling impurity solver. The interaction quench calculations reveal the phonon-assisted...
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In: Physical Review B, 2013, vol. 88, no. 12, p. 125126
We study the Holstein-Hubbard model at half filling to explore ordered phases including superconductivity (SC), antiferromagnetism (AF), and charge order (CO) in situations where the electron-electron and electron-phonon interactions are strong (comparable to the electronic bandwidth). The model is solved in the dynamical mean-field approximation with a continuous-time quantum Monte Carlo...
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