Pair breaking by nonmagnetic impurities in the noncentrosymmetric superconductor CePt₃ Si

We have studied the effect of Ge substitution and pressure on the heavy-fermion superconductor CePt₃ Si. Ge substitution on the Si site acts as negative chemical pressure leading to an increase in the unit-cell volume but also introduces chemical disorder. We carried out electrical resistivity and ac heat-capacity experiments under hydrostatic pressure on CePt₃ Si_1-x Ge_x (x=0,0.06). Our experiments show that the suppression of superconductivity in CePt₃ Si _1-x Ge_x is mainly caused by the scattering potential, rather than volume expansion, introduced by the Ge dopants. The antiferromagnetic order is essentially not affected by the chemical disorder.