ELECTRON-TRANSPORT IN DIRTY MULTICHANNEL SYSTEMS

We study the temperature dependence of the conductance and of the cond uctivity of a doped two-chain ladder system in the presence of a barri er or of a low impurity concentration, respectively, focusing on the e ffects of electron-electron interaction. Like in the purely 1-D case, the conductance vanishes at low temperature when the Luttinger-liquid exponent K-rho,K-+ (for even-charge modes) is smaller than unity, desp ite the presence of dominant superconducting correlations. However, th ere is a region of repulsive interaction where perfect transmission ac ross the barrier occurs. This is due to a renormalization of K-rho,K- produced by the difference in Fermi velocities of the bonding and ant ibonding bands.