title: Test of the Wiedemann-Franz law in an optimally doped cuprate.
abstract: We present a study of heat and charge transport in Bi(2+x)Sr(2-x)CuO(6+delta) focused on the size of the low-temperature linear term of the thermal conductivity at optimal-doping level. In the superconducting state, the magnitude of this term implies a d-wave gap with an amplitude close to what has been reported. In the normal state, recovered by the application of a magnetic field, measurement of this term and residual resistivity yields a Lorenz number L=kappa(N)rho(0)/T=1.3+/-0.2L(0). The departure from the value expected by the Wiedemann-Franz law is thus slightly larger than our estimated experimental resolution.
authors.affiliation: Laboratoire de Physique Quantique (CNRS), ESPCI, 10 Rue de Vauquelin, 75231 Paris, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Bel
authors.forename: Kamran
authors.initials: K
authors.lastname: Behnia
authors.forename: Cyril
authors.initials: C
authors.lastname: Proust
authors.forename: Peter
authors.initials: P
authors.lastname: van der Linden
authors.forename: Duncan
authors.initials: D
authors.lastname: Maude
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Vedeneev