Novel phase diagram of antiferromagnetism and superconductivity in CeRhIn5

We report on the pressure (P)-induced phase diagram of antiferromagnetism (AFM) and superconductivity (SC) which emerges at their border at zero magnetic field. The nuclear-quadrupole-resonance (NQR) measurements have revealed that AFM can take place in the superconducting state with Tc∼2.1K at P=2.05GPa. The present experiments have, for the first time, demonstrated that AFM phase, AFM+SC uniformly coexisting phase, SC phase and paramagnetic phase all contact with each other at Ttetra∼2.1K and Ptetra∼2GPa which evidence the existence of the tetracritical point in the P-T phase diagram of AFM and SC in CeRnIn5