Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 18: Superconductivity - Properties, Electronic Structure, Order Parameter II

TT 18.9: Talk

Monday, March 7, 2005, 12:30–12:45, TU H2053

In-plane angular dependence of the upper critical field of the unconventional superconductor CeCoIn₅ - Implications for the order parameter symmetry — •F. Weickert¹, P. Gegenwart¹, S. Haas², H. Won³, and K. Maki² — ¹Max Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, 01187 Dresden, Germany — ²Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484, USA — ³Department of Physics, Hallym University, Chunchon 200-702, South Korea

CeCoIn₅ is a tetragonal heavy fermion system that shows unconventional superconductivity below T_c  = 2.3K with upper critical fields of about 5T (B || c) and 11.5T (B ⊥ c). Below a temperature of 0.7K, the superconducting to normal transition is of first order and at lower temperatures indications for an inhomogenous Fulde-Ferrell-Larkin-Ovchinnikov state in close vicinity to B_c2 (T) have been discovered.

Here we use resistivity measurements to study the in-plane angular dependence of the upper critical field B_c2 (θ) at 0.1K. A fourfold oscillation with 2% amplitude is observed. Since B_c2 for fields parallel to the [110] direction is larger than along the [100] direction, our results would be compatible with a d_xy superconducting order parameter.