Effects of two gaps and paramagnetic pair breaking on the upper critical field of SmFeAsO0.85 and SmFeAsO0.8F0.2 single crystals


Effects of two gaps and paramagnetic pair breaking on the upper critical field of SmFeAsO0.85 and SmFeAsO0.8F0.2 single crystals

Lee, H.-S.; Bartkowiak, M.; Park, J.-H.; Lee, J.-Y.; Kim, J.-Y.; Sung, N.-H.; Cho, B. K.; Jung, C.-H.; Kim, J. S.; Lee, H.-J.

We investigated the temperature dependence of the upper critical field [Hc2(T)] of fluorine-free SmFeAsO0.85 and fluorine-doped SmFeAsO0.8F0.2 single crystals by measuring the resistive transition in low static magnetic fields and in pulsed fields up to 60 T. Both crystals show that Hc2(T)’s along the c axis [Hc2 c(T)] and in an ab-planar direction [Hc2 ab(T)] exhibit a linear and a sublinear increase, respectively, with decreasing temperature below the superconducting transition. Hc2(T)’s in both directions deviate from the conventional one-gap Werthamer-Helfand-Hohenberg theoretical prediction at low temperatures. A two-gap nature and the paramagnetic pair-breaking effect are shown to be responsible for the temperature-dependent behavior of Hc2 c and Hc2 ab, respectively.

  • Physical Review B 80(2009), 144512

Permalink: https://www.hzdr.de/publications/Publ-13545
Publ.-Id: 13545