Colloquim in Department of Physics, Okayama University

Title	Evidence for Spin-Fluctuation-Mediated Superconductivity in Electron-Doped Cuprates
Speaker	Prof. Nigel Hussey ( University of Bristol, UK and Radboud University, Netherlands)
Date/Time	12th July, 14:00-15:00
Place	Room 21 in the Main Building
Abstract	In conventional, phonon-mediated superconductors, the transition temperature Tc and normal-state scattering rate 1/t - deduced from the linear-in-temperature resistivity ρ(T) - are linked through the electron-phonon coupling strength lph. In cuprate high-Tc superconductors, no equivalent λ has yet been identified, despite the fact that at high doping, α - the low-T T -linear coefficient of ρ(T) - also scales with Tc. Here, we use high-field magnetoresistance to extract 1/t in electron-doped La2−xCexCuO4 (LCCO) as a function of x from near-optimal doping to beyond the superconducting dome. A highly anisotropic inelastic component to 1/t is revealed whose magnitude diminishes tenfold across the doping series. Using known Fermi surface parameters and subsequent modelling of the Hall coefficient, we demonstrate that the form of 1/t in LCCO is consistent with scattering off commensurate antiferromagnetic spin fluctuations of variable strength lsf. The clear correlation between α, lsf and Tc then identifies low-energy spin-fluctuations as the primary pairing glue in electron-doped cuprates. The contrasting magnetotransport behaviour in hole-doped cuprates suggests that the higher Tc in the latter cannot be attributed solely to an increase in lsf. Indeed, the success in modelling LCCO serves to reinforces the notion that resolving the origin of high-temperature superconductivity in hole-doped cuprates will require more than a simple extension of BCS theory. leaflet
世話人	笠原　成（内線 7828）