Events

Seminar of International Laboratory of High Magnetic Fields and Low Temperatures PAS

Measurements of H_c1,specific heat and determination the type of symmetry from the London penetration depth  in Fe-based superconducting compounds

V. A. Vlasenko

P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia

One of the most outstanding issue for the Fe-based superconducting materials is the symmetry of the superconducting (SC) state. The pairing symmetry in the Fe-based pnictides is under debate and various scenarios are discussed. There is no general consensus on the nature of pairing at the moment. For instance, the bulk probes, such as specific heat, Andreev reflections spectroscopy, thermal conductivity, and penetration depth λ−2ab (T) for FeSe pointed to the existence of two-gap nodeless superconductivity. In contrast, evidence for nodal superconductivity in FeSe is reported from the surface-sensitive probe, such as scanning tunneling spectroscopy. The T- dependence of λ−2ab is directly determined by the gap function. Based on the comprehensive low-T measurements of the magnetic penetration depth and specific heat, we provide evidence for two energy gaps in Fe(Se,S).