Specific heat and ac susceptibility studies of the superconducting phase diagram of PrOs4Sb12

Abstract

We report on ac-susceptibility and heat-capacity measurements of the superconductor PrOs4Sb12 in magnetic fields. The resulting phase diagram reveals two distinguishable superconducting phases with transitions at the upper critical field Bc2 and a slightly lower field Bc2*. Between Bc2* and 0.7×Bc2* the ac-susceptibility data shows a region with enhanced pinning properties characterized by an extended peak effect. The heat-capacity data reveal an extremely strongly coupled superconductivity with a considerable contribution of heavy quasiparticles. This unusual strong-coupling behavior originates in a sharp increase of the superfluid density at Tc. The decrease of the discontinuity of the specific heat at Tc and the corresponding pronounced increase of the Ginzburg-Landau-Maki parameter κ2 indicate that the superconductivity is most probably not Pauli limited in a large temperature range.

Source-reported materials — not catalogue approval

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