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TT: Tiefe Temperaturen

TT 9: Neue und unkonventionelle Supraleiter

TT 9.11: Talk

Tuesday, March 25, 2003, 12:00–12:15, HSZ301

Alternative approach to the order parameter symmetry in Sr₂RuO₄: Orbital-singlet pairing — •Ralph Werner — Institut für Theorie der Kondensierten Materie, Universität Karlsruhe, D-76128 Karlsruhe, Germany

Based on the degeneracy of the d_zx and d_yz orbitals and Hund’s rule coupling it is shown that the Cooper pairs may well condense in orbital singlets [1]. Together with the spin-triplet wave functions the real-space wave function then is symmetric. Considering interaction effects via the symmetry of the bosonized description of the in-plane electron correlations the order parameter is argued to have A_1g symmetry consistent with a number of experimental observations. The different components of the order parameter give rise to the two-dimensional gapless fluctuations detected via the specific heat, NQR, and thermal transport measurements. The sensitivity of the material on non-magnetic impurities follows in a straightforward manner from the orbital-singlet configuration. It is shown that the approach is in many aspects similar to the widely discussed p-wave picture [2] and thus provides a complementary rather than competing viewpoint.

[1] R. Werner, cond-mat/0208307, Phys. Rev. B, in print (2003).

[2] M. Sigrist et al., Physica C 317-318, 134 (1999).