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TT: Tiefe Temperaturen

TT 10: Supraleitung: Theorie

TT 10.2: Vortrag

Dienstag, 12. März 2002, 10:30–10:45, H18

Electronic theory for superconductivity in Sr₂RuO₄: triplet pairing due to spin-fluctuation exchange — •Ilya Eremin, Dirk Manske, Christian Joas, and Karl Bennemann — Institut fuer Theoretische Physik, Freie Universitaet Berlin, D-14195 Berlin

Using the Hubbard Hamiltonian for the three electronic bands crossing the Fermi level in Sr₂RuO₄ we calculate the dynamical spin susceptibility χ(q, ω) in quantitative agreement with nuclear magnetic resonance (NMR) and inelastic neutron scattering (INS) experiments. The calculated susceptbility has two peaks at Q_i = (2π/3, 2π/3) due to nesting properties of the Fermi surface belonging to the α- and β-bands and at q_i = (0.2π, 0) due to the tendency towards ferromagnetism of the γ-band. Nesting is stronger for out-of-plane χ_⊥(q,ω). Applying spin-fluctuation exchange theory for Cooper-pairing as in layered cuprates we determine from the Fermi surface topology and the elementary excitations that superconductivity in Sr₂RuO₄ consists of triplet pairing. Thus we can exclude s− and d−wave symmetry for the superconducting order parameter. We find a superconducting gap with nodes between RuO₂ planes.