Symmetry of Order Parameters in Multiband Superconductors LaRu4As12 and PrOs4Sb12 Probed by Local Magnetization Measurements

J. Juraszek, R. Wawryk, Z. Henkie, M. Konczykowski, and T. Cichorek

The temperature dependencies of the lower critical field H_c1(T) of several filled-skutterudite superconductors were investigated by local magnetization measurements. We attribute the unusual H_c1(T) dependencies of LaRu₄As₁₂ and PrOs₄Sb₁₂ to a kink structure in their superfluid densities due to different contributions from two nearly decoupled bands. Whereas LaRu₄As₁₂ is established as a two-band isotropic s-wave superconductor, nonsaturating behavior of H_c1(T) is observed for PrOs₄Sb₁₂ , indicative of an anisotropic structure of a smaller gap. For this superconductor with broken time-reversal symmetry, our findings suggest a superconducting state with multiple symmetries of the order parameters.