LOCALIZATION, SUPERCONDUCTIVITY AND MAGNETIC-FIELD IN A QUASI-1D CONDUCTOR

We show that the quasi-ID aspect of the electronic motion leads to new developments in the physics of localization. In a conductor with an o pen Fermi surface, the magnetic field makes the electronic motion more and more one-dimensional, in the sense that it confines the wave func tions on the chains. Therefore, the effect of disorder is stronger whe n the field is increased. As a consequence, a strong magnetic field in duces a crossover to a ID localized state. We also extend the original work of A.G. Lebed' on the phase diagram of BCS quasi-ID superconduct ors in a magnetic field. The usual Ginzburg-Landau regime is followed, when increasing the field, by a series of superconducting phases. The first order transitions between these phases are related to. commensu rability effects between the periodicity of the order parameter and th e distance between chains. The order parameter and the current distrib ution of these new phases show a new symmetry (of laminar type) which has never been observed or predicted in other systems.