A. A. Katanin

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Using the one-loop functional renormalization group technique, we evaluate the self-energy in the weak-coupling regime of the 2D t-t(') Hubbard model. At van Hove (vH) band fillings and at low temperatures, the quasiparticle weight along the Fermi surface (FS) continuously vanishes on approaching the (pi,0) point where the quasiparticle concept is invalid.(More)
Phase diagrams of the two-dimensional one-band t-t8 Hubbard model are obtained within the two-patch and temperature-cutoff many-patch renormalization group approaches. At small t8 and at van Hove band fillings antiferromagnetism dominates, while with increasing t8 or changing filling antiferromagnetism is replaced by d-wave superconductivity. Near t85t/2(More)
Isotropic S = 1/2 quasi-one-dimensional antiferromagnets are considered within the bosonization method. The 1/z⊥-corrections to the interchain meanfield theory (where z⊥ is the number of nearest neighbors in transverse to chain directions) are obtained for the ground-state sublattice magnetization S0 and Neel temperature TN . The corrections to TN make up(More)
By means of the dynamical vertex approximation (DΓA) we include spatial correlations on all length scales beyond the dynamical mean-field theory (DMFT) for the half-filled Hubbard model in three dimensions. The most relevant changes due to nonlocal fluctuations are (i) a deviation from the mean-field critical behavior with the same critical exponents as for(More)
The Bethe-Salpeter equation is combined with the temperature-cutoff functional renormalization group approach to analyze the order parameter structure for the leading instabilities of the 2D t-t Hubbard model. We find significant deviations from the conventional s-, p-, or d-wave forms, which is due to the frustration of antiferromagnetism at small and(More)
We present a novel scheme for an unbiased, nonperturbative treatment of strongly correlated fermions. The proposed approach combines two of the most successful many-body methods, the dynamical mean field theory and the functional renormalization group. Physically, this allows for a systematic inclusion of nonlocal correlations via the functional(More)
We consider an effect of weak impurities on the electronic properties of graphene within the functional renormalization-group approach. The energy dependences of the electronic self-energy and density of states near the neutrality point are discussed. Depending on the symmetry of the impurities, the electronic damping and density of states ρ can deviate(More)
Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d or f orbitals, which leads to the formation of local magnetic moments. The combination of these(More)
We use the quasistatic approach to analyze the criterion of ferromagnetism for two-dimentional (2D) systems with the Fermi level near Van Hove singularities (VHS) of the electronic spectrum. It is shown that the spectrum of spin excitations (paramagnons) is positively defined when the interaction I between electrons and paramagnons, which corresponds to the(More)
We discuss the low-temperature behavior of the electronic self-energy in the vicinity of a ferromagnetic instability in two dimensions within the twoparticle self-consistent approximation, functional renormalization group and Ward-identity approaches. Although the long-range magnetic order is absent at T > 0, the self-energy has a non-Fermi liquid form at(More)