title: Pairing of Cooper pairs in a fully frustrated Josephson-junction chain.
abstract: We study a one-dimensional Josephson-junction chain embedded in a magnetic field. We show that, when the magnetic flux per elementary loop equals half the superconducting flux quantum phi0 = h/2e, a local Z2 symmetry arises. This symmetry is responsible for a nematic Luttinger liquid state associated with bound states of Cooper pairs. We analyze the phase diagram and discuss some experimental possibilities to observe this exotic phase.
authors.affiliation: Laboratoire de Physique de la Matière Condensée, CNRS UMR 8551, Ecole Normale Supérieure, 24, rue Lhomond, 75231 Paris Cedex 05, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Douçot
authors.forename: Julien
authors.initials: J
authors.lastname: Vidal