Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 67: Correlated Electrons: f-Electron Systems
TT 67.3: Talk
Wednesday, March 18, 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 Tc≈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 (Tc 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.