arXiv:cond-mat/0105564 · Physical review. B, Condensed matter
Violation of the Fermi-liquid picture in two-dimensional systems owing to Van Hove singularities
V. Yu. Irkhin, A. A. Katanin
Abstract
We consider the two-dimensional $t\ensuremath{-}{t}^{\ensuremath{'}}$ Hubbard model with the Fermi level being close to Van Hove singularities. The phase diagram of the model is discussed. Far from the quantum phase transition (QPT) into ferro- (antiferro-) magnetic states, the self-energy at the singularity points has a nearly linear energy dependence, the density of states being proportional to ${\mathrm{ln}}^{3}|\ensuremath{\varepsilon}|.$ In the quantum-disordered and quantum-critical regimes near the QPT a scaling approach is used. At small energies the self-energy demonstrates a powerlike behavior with the exponent changing from unity to zero in a narrow energy interval. Provided that the system is close to ferromagnetic instability which occurs at ${t}^{\ensuremath{'}}/\stackrel{\ensuremath{\rightarrow}}{t}\ensuremath{-}1/2,$ the quasiparticle spectral weight has, instead of a narrow peak, a broad maximum and is nonmonotonous at small energies. The application of the results to cuprates is discussed.