Magnetic excitations in Kondo liquid: Superconductivity and Hidden Magnetic Quantum Critical Fluctuations

TL;DR

This study investigates magnetic excitations and quantum critical fluctuations in the heavy electron superconductor CeCoIn$_5$, revealing insights into its pairing mechanism and similarities with high-temperature cuprate superconductors.

Contribution

It provides experimental evidence of magnetic quantum critical fluctuations and their role in superconductivity in CeCoIn$_5$, highlighting the presence of an antiferromagnetic QCP and similarities with cuprates.

Findings

Heavy electron Kondo liquid behavior aligns with BCS theory.

Presence of 2D magnetic quantum critical fluctuations.

Antiferromagnetic QCP located at slightly negative pressure.

Abstract

We report Knight shift experiments on the superconducting heavy electron material CeCoIn$_5$ that allow one to track with some precision the behavior of the heavy electron Kondo liquid in the superconducting state with results in agreement with BCS theory. An analysis of the $^{115}$In nuclear quadrupole resonance (NQR) spin-lattice relaxation rate $T_1^{-1}$ measurements under pressure reveals the presence of 2d magnetic quantum critical fluctuations in the heavy electron component that are a promising candidate for the pairing mechanism in this material. Our results are consistent with an antiferromagnetic quantum critical point (QCP) located at slightly negative pressure in CeCoIn$_5$ and provide additional evidence for significant similarities between the heavy electron materials and the high $T_c$ cuprates.