Structurally tuned superconductivity in heavy-fermion CeMIn 5 (MCo, Ir, Rh)

Abstract

We discuss systematic trends in the high-temperature physical properties of the heavy Fermion superconductors (HFS) CeCoIn 5 (T c =2.3 K , γ=300 mJ/ mol K 2 ), CeIrIn 5 (T c =0.4 K , γ=750 mJ/ mol K 2 ), and CeRhIn 5 (P c =16 kbar , T c =2.1 K , γ=400 mJ/ mol K 2 ) in terms of crystalline-electrical-field effects(CEF). We suggest the possibility that the interplay between the symmetry of the CEF ground-state (or low- T CEF scheme of levels) and the f–s hybridization could generate spin fluctuations relevant to the superconducting pairing mechanism in these materials. This hypothesis may provide insight into the fact that some crystal structures appear to favor superconductivity. Further, CeMIn 5 (MCo, Ir, Rh) appear to be structural relatives of the cubic heavy Fermion superconductor CeIn 3, but with much higher T c's. We argue that structural layering inherent in the tetragonal CeMIn 5 crystal structure determines the magnetic and electronic anisotropy responsible for the enhanced T c's. We also describe similarities and differences between these compounds and the high- T c cuprates.