Weak coupling instabilities of two-dimensional lattice electrons

Binz, Benedikt; Baeriswyl, Dionys; Douçot, B.

doi:10.1016/j.physc.2004.02.145

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Journal article

Weak coupling instabilities of two-dimensional lattice electrons

Binz, Benedikt Department of Physics, University of Fribourg, Switzerland - Theoretische Physik, ETH Zürich, Switzerland
Baeriswyl, Dionys Department of Physics, University of Fribourg, Switzerland
Douçot, B. Laboratoire de Physique Théorique et Hautes Energies, CNRS Universités Paris VII, France

10.05.2004

Published in:

Physica C: Superconductivity. - 2004, vol. 408-410, p. 250-251

English We present a consistent and systematic study of a two-dimensional extended Hubbard model in the weak coupling limit. Quite generally, the electron gas is unstable towards a superconducting state even in the absence of phonons, since high-energy spin fluctuations create an effective attraction between the quasi-particles. However in the special case of a half-filled nearest-neighbor tight-binding band, the Fermi surface is nested and the system is at a Van Hove singularity. In this situation, there are six competing instabilities: s- and d-wave superconductivity, spin- and charge-density waves and two phases with circulating charge and spin currents, respectively. The required renormalization group formalism can be presented on a most elementary level, connecting the idea of the "parquet summation" to the more modern concept of Wilson's effective action. As a result, a rich phase diagram is obtained as a function of the model interaction. We also argue that the one-loop approximation is insufficient in a case where the Fermi surface is at a Van Hove singularity but not nested.

Faculty

Faculté des sciences et de médecine

Department

Département de Physique

Language