Coexistence of antiferromagnetism and superconductivity in CeRhIn5 under high pressure and magnetic field

New light is shed on the interplay between antiferromagnetism and superconductivity by a detailed study of the phase diagram of CeRhIn5 under high pressure and magnetic field using ac calorimetry. In zero field, the antiferromagnetic order vanishes suddenly above p(c)(star)=2 GPa leading to a pure superconducting ground state. An inhomogeneous superconducting phase transition is found below p(c)(star). Above p(c)(star), the application of an external magnetic field H parallel to ab induces a second transition, which suggests the reentrance of antiferromagnetism, its coexistence with superconductivity, and also the important role of the vortices. This field-induced supplementary state vanishes around the expected quantum critical point, which will occur in the absence of superconductivity.