CeIrIn5: Superconductivity on a magnetic instability

Abstract

We report the doping-induced antiferromagnetic state and Fermi liquid state that are connected by a superconducting region in a series of CeIrIn5−xHgx, CeIrIn5−xSnx and CeIr1−xPtxIn5 single crystals. Measurements of the specific heat C(T ) and electrical resistivity ρ(T ) demonstrate that hole doping via Hg/In substitution gives rise to an antiferromagnetic ground state, but substitutions of In by Sn or Ir by Pt (electron doping) favor a paramagnetic Fermi liquid state. A cone-like non-Fermi liquid region is observed near CeIrIn5, showing a diverging effective mass on the slightly Hg-doped side. The obtained temperature-doping phase diagram suggests that CeIrIn5 is in proximity to an antiferromagnetic quantum critical point, and heavy fermion superconductivity in this compound is mediated by magnetic quantum fluctuations rather than by valence fluctuations.

Reemergent Superconductivity and Avoided Quantum Criticality in Cd-DopedCeIrIn5under Pressure

“…NMR [17] as well as thermodynamic and transport measurements [18] are consistent with CeIrIn 5 being in close proximity to an AFM QCP, which suggests a magnetic pairing mechanism. In contrast, nuclear quadrupole (NQR) experiments have been interpreted as providing evidence for pairing mediated by valence fluctuations [19].…”

“…well as thermodynamic and transport measurements [18], and now the similarity in the pressure responses of Cd-doped CeCoIn 5 and CeIrIn 5 provide a compelling body of evidence for magnetic pairing in CeIrIn 5 . We take this point of view, but now must ask how should the phase diagram in Fig.…”

Unconventional superconductivity

“…Shang et al [247] doped both Hg and Sn on the In site as well as Pt on the Ir site. They find a maximum in the specific heat  (proportional to the effective mass, m*) at about CeIr(In0.97Hg0.03)5 and suggest that pure CeIrIn5 is therefore "in proximity" to an antiferromagnetic quantum critical point.…”

Physical properties of Cd doped CeIrIn5 under pressure

“…Nuclear quadrupole resonance (NQR) measurement of Cd doped CeIrIn5 suggests a valence instability contributes to the SC2 [10]. On the other hands, nuclear magnetic resonance (NMR) and transport measurements suggest CeIrIn5 is in the vicinity of AFM QCP [11][12][13][14][15]. In order to clarify the relationship between SC and magnetic instability in CeIrIn5, we measured the electrical resistivity of Cd doped CeIrIn5 under pressure.…”