The quantum critical point in CeRhIn₅: A resistivity study

The pressure-temperature phase diagram of CeRhIn₅ has been studied under high magnetic field by resistivity measurements. Clear signatures of a quantum critical point has been found at a critical pressure of p _c ≈ 2:5 GPa. The field induced magnetic state in the superconducting state is stable up to the highest measured field. At p _c the antiferromagnetic ground-state under high magnetic field collapses very rapidly. Clear signatures of p_c are the strong enhancement of the resistivity in the normal state and of the inelastic scattering term. No clear T² temperature dependence could be found for pressures above T_c. From the analysis of the upper critical field within a strong coupling model we present the pressure dependence of the coupling parameter λ and the gyromagnetic ratio g. No signatures of a spatially modulated order parameter could be evidenced. A detailed comparison with the magnetic field-temperature phase diagram of CeCoIn₂ is given. The comparison between CeRhIn₂ and CeCoIn₂ points out the importance to take into account the field dependence of the effective mass in the calculation of the superconducting upper critical field H _c2. It suggests also that when the magnetic critical field H _M(0) becomes lower than H_c2(0), the persistence of a superconducting pseudo-gap may stick the antiferromagnetism to H _c2(0).