Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.28: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

Unconventional strain dependence of superconductivity in Sr₂RuO₄ — •Sebastian Zaum^1,2, Kai Grube¹, Roland Schäfer¹, Florian Hübler¹, Christoph Meingast¹, Yoshiteru Maeno³, and Hilbert v. Löhneysen^1,2 — ¹Karlsruher Institut für Technologie, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — ²Karlsruher Institut für Technologie, Physikalisches Institut, 76131 Karlsruhe, Germany — ³Department of Physics, Kyoto University, Kyoto 606-8502, Japan

In the transition-metal oxide Sr₂RuO₄ unconventional superconductivity emerges presumably near a ferromagnetic ground state. As a result it is generally believed that critical magnetic fluctuations form the pairing mechanism leading to p-wave symmetry of the order parameter. To investigate the coupling of superconductivity to the crystal lattice we measured the thermal expansion of Sr₂RuO₄ single crystals in a temperature range between 20 mK and 10 K. The uniaxial pressure and strain dependences of the superconducting transition temperature along the tetragonal a and c axes were determined by using the Ehrenfest relation and the elastic constants. Although the layered crystal structure suggests a strongly anisotropic behavior, the strain dependences of T_c are nearly of the same size for both axes. In contrast to many conventional superconductors, the temperature dependence of the linear thermal expansion coefficients along the a and c axes are not proportional to each other. Such a difference indicates that the superconducting ground state is controlled by more than one characteristic energy scale.