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TT: Fachverband Tiefe Temperaturen
TT 7: SC: Properties, Electronic Structure, Mechanisms 2
TT 7.6: Talk
Monday, March 14, 2011, 15:15–15:30, HSZ 301
Order parameter in CeCu2Si2 — •Hugo A. Vieyra1, Manuel Brando1, Niels Oeschler1, Silvia Seiro1, Hirale S. Jeevan2, Christoph Geibel1, David Parker3, and Frank Steglich1 — 1Max Planck Institute for Chemical Physics of Solids, Dresden 01187, Germany — 2I. Physik. Institut, Georg-August-Universität Göttingen, Göttingen 37077, Germany — 3US Naval Research Laboratory. Washington, DC 20375, USA
Understanding the interplay between magnetism and unconventional superconductivity remains a key challenge in solid-state physics. A clear example is the archetypical heavy-fermion compound CeCu2Si2 which exhibits superconductivity (Tc=600 mK) in the vicinity of a magnetic quantum critical point. It is believed that magnetic fluctuations mediate superconductivity and its order parameter possesses d-wave symmetry, both ideas still under debate. In this work, a high-quality single crystal with a purely superconducting ground state (S type) has been chosen to investigate the low-temperature thermal- and electric-transport characteristics of the superconducting state. Non-vanishing contributions of low-energy quasiparticle excitations to the thermal transport (κ0/T>0) suggest the presence of nodal structure in CeCu2Si2. In turn, angle-dependent resistivity measurements of the upper critical field Hc2 point towards unconventional superconductivity with d-wave symmetry of the order parameter. Theoretical calculations reveal the strong influence of Pauli paramagnetic effects and a dxy symmetry of the gap function.