Heat transport study of field-tuned quantum criticality in CeIrIn5

TL;DR

This study investigates heat and charge transport in CeIrIn5 near quantum criticality, revealing Fermi liquid behavior and a weak magnetic field response, contrasting with related compounds and indicating a more localized electron state.

Contribution

The paper provides the first detailed measurements of thermal and electrical conductivity in CeIrIn5 under magnetic fields, demonstrating Fermi liquid behavior and a reduced proximity to quantum criticality compared to CeCoIn5.

Findings

Wiedemann-Franz law holds above Hc2

Electrical and thermal resistivities follow T^2 dependence

CeIrIn5 is farther from quantum critical point than CeCoIn5

Abstract

The in-plane electrical resistivity, rho, and thermal conductivity, kappa, of the heavy-fermion superconductor CeIrIn5 were measured down to 40mK in magnetic fields up to 11 T applied along the c axis. For all fields above Hc2=4T of filamentary superconductivity, we find that the ratio of heat and charge conductivities in the T to 0 limit obeys the Wiedemann-Franz law, kappa/T=L0/rho, where L0 = 2.45*10^-8 WOhmK^-2 is the Sommerfeld value of the Lorenz number. The temperature-dependent parts of both the electrical and thermal resistivity,w = T/L0 kappa, follow the functional dependence expected for the Fermi liquid theory of metals with rho - rho_0 = AT^2, w - w_0 = BT^2, with rho0 = 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 gamma_0 in CeIrIn5 is twice as large as gamma_0 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.