Pressure-induced novel superconductivity and heavy fermion state in rare earth compounds

We have carried out the electrical resistivity measurements under high pressures up to 24 GPa for CeTX₃ (T: Co and Ir, X: Si and Ge), CePd₅Al₂ and YbIr₂Zn₂₀ in order to investigate quantum criticality and superconductivity. Antiferromagnets CeTX₃ with the non-centrosymmetric tetragonal structure show superconductivity under high pressures and reveal a huge upper critical field for H∥ [001]. An antiferromagnet CePd₅Al₂, which is an isostructural family of a heavy fermion superconductor NpPd₅Al ₂, also shows superconductivity under high pressures. In these compounds, superconductivity appears in the vicinity of quantum critical point. On the other hand, YbIr₂Zn₂₀ without magnetic ordering approaches to the quantum critical point with increasing pressure and exhibits a super-heavy fermion state exceeding 10 J/(K²· mol).