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TT: Fachverband Tiefe Temperaturen

TT 67: Correlated Electrons: f-Electron Systems

TT 67.3: Vortrag

Mittwoch, 18. März 2015, 15:30–15:45, H 3005

Measuring the T-dependence of the penetration depth of CeCu₂Si₂ with superconducting microwave resonators at mK temperatures — •Markus Thiemann¹, Martin Dressel¹, Marc Scheffler¹, Silvia Seiro², Christoph Geibel², and Frank Steglich² — ¹1. Physikalisches Institut, Universität Stuttgart, Germany — ²Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany

Microwave measurements on superconductors can reveal the temperature dependence of the penetration depth, which can indicate the presence of nodes in the superconducting gap function. CeCu₂Si₂ is a heavy-fermion superconductor with critical temperature T_c≈0.6 K. Though CeCu₂Si₂ for a long time was believed to be a d-wave superconductor, at present it is under debate whether its order parameter features nodes or not.

Therefore, we have performed microwave measurements to study the penetration depth, but we address the microwave surface resistance as well. To be able to probe superconducting bulk samples at mK temperature, we have developed a new experimental approach based on superconducting stripline resonators. We evaluate the performance of this technique at temperatures down to 30 mK by studying the conventional superconductor zirconium (T_c similar to that of CeCu₂Si₂). Comparing our data on the penetration depth of a CeCu₂Si₂ single crystal with that of zirconium, we find a clear difference in the temperature dependence, which we discuss in terms of possible nodes or multiband superconductivity.