Theoretical study of the role of interchain processes in coupled Luttinger liquids ; Etude théorique du rôle des processus interchaînes dans des liquides de Luttinger couplés

Membres du jury: Erik Sorensen, Claude Bourbonnais, Thierry Giamarchi, Didier Poilblanc, Leonardo Degiorgi, Denis Jerome ; One-dimensional metallic systems are characterized by a very peculiar behaviour: the Luttinger liquid phase. The physical properties of such a system are well understood from a theoretical point of view and are quite different from the usual metallic phase in two and three dimensions, which is known as the Fermi liquid. Moreover, this description may be relevant to many experimental devices. However, the role of the interchain coupling is still not clear and the observation of the Luttinger liquid phase may be restricted to certain values of the physical parameters (temperature, pressure and so on) due to this coupling. It has been proposed that the interchain coupling might be reduced due to the interactions. By using numerical techniques and scaling laws, we demonstrate the validity of such an approach for microscopic lattice models and we obtain in a \emph(quantitative) way the renormalisation of the interchain coupling in some regime. Moreover, the effect of the particle-hole pair hopping is shown, for the first time with microscopic models, to be relevant for highly correlated coupled chains. We also study the various excitations that exist near the metal-insulator transition. Transport properties are also discussed for these materials and compared to the theoretical results obtained with an adequate hamiltonian. Here again, the strong interactions are responsible for the strong suppression of the optical absorption which is indeed observed in these materials. ; Les systèmes métalliques unidimensionnels possèdent une physique bien particulière désignée par le terme de «liquide de Luttinger». Les propriétés d'un tel système sont bien comprises du point de vue théorique et diffèrent énormément du comportement métallique en deux et trois dimensions qui est décrit par le liquide de Fermi. En outre, il existe de nombreuses réalisations expérimentales potentielles susceptibles d'être décrites ...