NMR Evidence of anisotropic Kondo liquid behavior in CeIrIn$_5$

TL;DR

This study uses NMR Knight shift measurements to reveal that the hybridization and Kondo liquid behavior in CeIrIn$_5$ are anisotropic, varying with magnetic field orientation, which may influence its unconventional superconductivity.

Contribution

It provides the first detailed evidence of anisotropic hybridization and Kondo liquid behavior in CeIrIn$_5$ through orientation-dependent Knight shift measurements.

Findings

Knight shift anomaly depends on field orientation

Crossover temperature T* varies with field direction

Hybridization is anisotropic, affecting superconductivity

Abstract

We report detailed Knight shift measurements of the two indium sites in the heavy fermion compound CeIrIn$_5$ as a function of temperature and field orientation. We find that the Knight shift anomaly is orientation-dependent, with a crossover temperature $T^*$ that varies by 50% as the field is rotated from (001) to (100). This result suggests that the hybridization between the Ce 4f states and the itinerant conduction electrons is anisotropic, a result that reflects its collective origin, and may lead to anisotropic Kondo liquid behavior and unconventional superconductivity.