Impact of isoelectronic substitution and hydrostatic pressure on the quantum critical properties of CeRhSi3.

There is an ongoing dispute in the community about the absence of a magnetic quantum critical point (QCP) in the noncentrosymmetric heavy fermion compound CeRhSi3. In order to explore this question we prepared single crystals of CeRh(Si1-xGex)3withx= 0.05 and 0.15 and determined the temperature-pressure (T-p) phase diagram by means of measurements of the electrical resistivity. The substitution of isoelectronic but large Ge enforces a lattice volume increase resulting in a weakening of the Kondo interaction. As a result, thex= 0.05 andx= 0.15 compound exhibit a transition into the antiferromagentic (AFM) at higher temperatures beingTN= 4.7 K andTN1= 19.7 K, respectively. Application of pressure suppressesTN(TN1) monotonically and pressure induced superconductivity is observed in both Ge-substituted compounds abovep≧ 2.16 GPa (x= 0.05) andp≧ 2.93 GPa (x= 0.15). Extrapolation ofTN(p) → 0 of CeRh(Si0.95Ge0.05)3yields a critical pressure ofpc≈ 3.4 GPa (in CeRh(Si0.85Ge0.15)3pc≈ 3.5 GPa) pointing to the presence of an AFM QCP located deep inside the superconducting state.