Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn$_{5}$

We report the dependence on pressure and magnetic field of the specific heat and electrical resistivity of the pressure-tuned heavy-fermion superconductor CeRhIn$_{5}$. Above a critical pressure, where long-range antiferromagnetic order (AFM) abruptly disappears, application of a field brings back magnetism inside the superconducting state. As a function of pressure at low temperatures, the set of fields required to induce magnetism defines a line of quantum-phase transitions that separates a phase of coexisting AFM and SC from a purely unconventional superconducting phase. This quantum-transition line and the upper critical field boundary, above which superconductivity is suppressed, merge at a quantum tetracritical point where another quantum-phase boundary separates magnetically ordered and disordered normal phases. The quasiparticle mass diverges as this normal-state quantum boundary is approached, and crossing it produces a change in the Fermi-surface volume. [1] [1] H. Shishido et al., J. Phys. Soc. Jpn. \textbf{74}, 1103 (2005).