Tuesday, March 27, 2012

1203.5567 (Y. Tokiwa et al.)

Quasiparticle entropy in the high-field superconducting phase of
CeCoIn$_5$
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Y. Tokiwa, E. D. Bauer, P. Gegenwart
The heavy-fermion superconductor CeCoIn$_5$ displays an additional transition within its superconducting (SC) state, whose nature is characterized by high-precision studies of the isothermal field dependence of the entropy, derived from combined specific heat and magnetocaloric effect measurements at temperatures $T\geq 100$ mK and fields $H\leq 12$ T aligned parallel, perpendicular and $18^\circ$ off the tetragonal [100] direction. For any of these conditions, we do not observe an additional entropy contribution upon tuning at constant temperature by magnetic field from the homogeneous SC into the presumed Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) SC state. By contrast, for $H\parallel [100]$ a negative isothermal entropy contribution, compatible with spin-density-wave (SDW) ordering, is found. Our data exclude the formation of a FFLO state in CeCoIn$_5$ for out-of-plane field directions, where no SDW order exists.
View original: http://arxiv.org/abs/1203.5567

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