SUPERCONDUCTIVITY OF QUASI-ONE-DIMENSIONAL CONDUCTORS IN A HIGH MAGNETIC-FIELD

We determine the phase diagram of a quasi-one-dimensional superconduct or (weakly coupled chains system with an open Fermi surface) in a magn etic field. A field H(0, H, 0) along the y direction (perpendicular th e direction x of highest conductivity) tends to confine the electronic motion in the z direction. At low temperature, this effect cannot be neglected and the Ginzburg-Landau theory breaks down. We find that the usual Ginzburg-Landau regime is followed, when the field is increased , by a cascade of superconducting phases separated by first-order tran sitions, which ends with a strong reentrance of the superconducting ph ase where the chains interact by Josephson coupling. This high-field s uperconductivity can survive even in the presence of Pauli pair breaki ng because the quasi-one-dimensional Fermi surface allows one to const ruct a Larkin-Ovchinnikov-Fulde-Ferrell state that can exist far above the Pauli-limited field. Moreover, elastic scattering does not destro y the superconducting phases in clean materials with sufficiently larg e anisotropy. We show that the superconducting state evolves from an A brikosov vortex lattice in weak field towards a Josephson vortex latti ce in the reentrant phase. Between these two limits, the order paramet er and the current distribution show laminar-type symmetry. The releva nce of our results is discussed for quasi-one-dimensional organic supe rconductors and quasi-two-dimensional superconductors.