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# Heat transport study of field-tuned quantum criticality in CeIrIn5 --- Physical Review B 93, 075116 (2016) / arXiv:1602.06311

Heat transport study of field-tuned quantum criticality in CeIrIn5

H. Shakeripour1,2,*, M. A. Tanatar2,†, C. Petrovic3,4, and Louis Taillefer2,4,‡

1.Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran

2.Département de Physique and RQMP, Université de Sherbrooke, Sherbrooke, Canada

3.Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA

4.Canadian Institute for Advanced Research, Toronto, Ontario, Canada

*hshakeri@cc.iut.ac.ir †Current address: Ames Laboratory, Ames, Iowa 50011, USA. ‡Louis.Taillefer@USherbrooke.ca

Physical Review B 93, 075116 (2016) / arXiv:1602.06311

#### ABSTRACT

The in-plane electrical resistivity, ρ, and thermal conductivity, κ, of the heavy-fermion superconductor CeIrIn5 were measured down to 40 mK in magnetic fields up to 11 T applied along the c axis. For all fields above Hc2=4 T of filamentary superconductivity, we find that the ratio of heat and charge conductivities in the T→0 limit obeys the Wiedemann-Franz law, κ/T=L0/ρ, where L0=2.45×10−8 WΩK−2 is the Sommerfeld value of the Lorenz number. The temperature-dependent parts of both the electrical and thermal resistivity, w≡T/L0κ, follow the functional dependence expected for the Fermi liquid theory of metals with ρ−ρ0=AT2, w−w0=BT2, with ρ0=w0 and B≈2A. The coefficient B does not show a significant field dependence even upon approaching Hc2=0.4 T of the bulk superconducting state. The weak response to the magnetic field is in stark contrast with the behavior found in the closely related CeCoIn5, in which the field-tuned quantum critical point coincides with Hc2. The value of the electron-electron mass enhancement, as judged by the A and B coefficients, is about one order of magnitude reduced in CeIrIn5 as compared to CeCoIn5 (in spite of the fact that the zero field γ0 in CeIrIn5 is twice as large as γ0 in CeCoIn5), which suggests that the material is significantly farther away from the magnetic quantum critical point at bulk Hc2 and at all of the studied fields. A suppressed Kadowaki-Woods ratio in CeIrIn5 compared to CeCoIn5 suggests a notably more localized nature of f electrons in the compound.