title: Isotope effect in superconducting n-doped SrTiO3.
abstract: We report the influence on the superconducting critical temperature Tcin doped SrTiO3of the substitution of the natural16O atoms by the heavier isotope18O. We observe that for a wide range of doping this substitution causes a strong (~50%) enhancement of Tc. Also the magnetic critical field Hc2is increased by a factor ~2. Such a strong impact on Tcand Hc2, with a sign opposite to conventional superconductors, is unprecedented. The observed effect could be the consequence of strong coupling of the doped electrons to lattice vibrations (phonons), a notion which finds support in numerous optical and photo-emission studies. The unusually large size of the observed isotope effect supports a recent model for superconductivity in these materials based on strong coupling to the ferroelectric soft modes of SrTiO3.
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Stucky
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: G W
authors.initials: GW
authors.lastname: Scheerer
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: Z
authors.initials: Z
authors.lastname: Ren
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Jaccard
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: J-M
authors.initials: JM
authors.lastname: Poumirol
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Barreteau
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Giannini
authors.affiliation: Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: van der Marel