title: Multiple gap symmetries for the order parameter of cuprate superconductors from penetration depth measurements.
abstract: The temperature dependence of the London penetration depth lambda was measured for an untwinned single crystal of YBa_{2}Cu_{3}O_{7-delta} along the three principal crystallographic directions (a, b, and c). Both in-plane components (lambda_{a};{-2} and lambda_{b};{-2}) show an inflection point in their temperature dependence which is absent in the component along the c direction (lambda_{c};{-2}). The data provide convincing evidence that the in-plane superconducting order parameter is a mixture of (s+d)-wave symmetry whereas it is mainly s wave along the c direction. In conjunction with previous results it is concluded that coupled s+d-order parameters are universal and intrinsic to cuprate superconductors.
authors.affiliation: Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Khasanov
authors.forename: S
authors.initials: S
authors.lastname: Strässle
authors.forename: D
authors.initials: D
authors.lastname: Di Castro
authors.forename: T
authors.initials: T
authors.lastname: Masui
authors.forename: S
authors.initials: S
authors.lastname: Miyasaka
authors.forename: S
authors.initials: S
authors.lastname: Tajima
authors.forename: A
authors.initials: A
authors.lastname: Bussmann-Holder
authors.forename: H
authors.initials: H
authors.lastname: Keller