Wilson's renormalization group applied to 2D lattice electrons in the presence of van Hove singularities |
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Authors: | B Binz D Baeriswyl B Douçot |
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Institution: | (1) Département de Physique, Université de Fribourg, Pérolles, 1700 Fribourg, Switzerland, CH;(2) Laboratoire de Physique de la Matière Condensée, école Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France and Laboratoire de Physique Théorique et Hautes énergies, Universités Paris VII, 4 Place Jussieu, 75252 Paris Cedex 05, France, FR |
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Abstract: | The weak coupling instabilities of a two dimensional Fermi system are investigated for the case of a square lattice using
a Wilson renormalization group scheme to one loop order. We focus on a situation where the Fermi surface passes through two
saddle points of the single particle dispersion. In the case of perfect nesting, the dominant instability is a spin density
wave but d-wave superconductivity as well as charge or spin flux phases are also obtained in certain regions in the space of coupling
parameters. The low energy regime in the vicinity of these instabilities can be studied analytically. Although saddle points
play a major role (through their large contribution to the single particle density of states), the presence of low energy
excitations along the Fermi surface rather than at isolated points is crucial and leads to an asymptotic decoupling of the
various instabilities. This suggests a more mean-field like picture of these instabilities, than the one recently established
by numerical studies using discretized Fermi surfaces.
Received 11 April 2001 and Received in final form 6 September 2001 |
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Keywords: | PACS 71 10 Fd Lattice fermion models (Hubbard model etc ) – 71 10 Hf Non-Fermi-liquid ground states electron phase diagrams and phase transitions in model systems – 74 72 -h High-Tc compounds |
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