Role of interchain coupling in linear conductors

Abstract

Renormalization-group methods are applied to a set of coupled linear chains in a model in which direct hopping between chains is excluded. Attention is focused on models in which intrachain interactions are repulsive. It is shown first for two chains and then for $N$ chains that a repulsive $\ensuremath{\delta}$-function intrachain interaction scales with decreasing temperature to the attractive fixed point. In the $N$-chain model this attractive fixed point is characterized by a charge-density wave whose phase is coherent between chains. A variety of response functions, spin and charge density wave at wave vector $2{k}_{F}$ (${k}_{F}$ is the Fermi wave vector), and excitonic response functions are calculated numerically. We also evaluate the uniform magnetic susceptibility and the charge-density-wave response at $4{k}_{F}$. A comparison is made to the behavior of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) at temperatures above 60 K. It is possible to qualitatively explain most of the behavior of this compound by assuming strong repulsion between electrons. A simple physical discussion of the strong-repulsion limit is given.