The interface between heavy fermions and normal electrons investigated by spatially-resolved nuclear magnetic resonance

TL;DR

This study uses spatially-resolved NMR to investigate how heavy-fermion superconductor layers interact with normal metal layers, revealing localized magnetic fluctuations and effects of interface symmetry breaking.

Contribution

It provides new insights into the spatial distribution of magnetic fluctuations and the influence of interfaces in heavy-fermion superlattices using site-selective NMR.

Findings

Magnetic fluctuations are confined to heavy-fermion layers.

Antiferromagnetic fluctuations decrease with thinner layers.

Interface effects significantly suppress magnetic fluctuations.

Abstract

We have studied the superlattices with alternating block layers (BLs) of heavy-fermion superconductor CeCoIn5 and conventional-metal YbCoIn5 by site-selective nuclear magnetic resonance(NMR) spectroscopy, which uniquely offers spatially-resolved dynamical magnetic information. We find that the presence of antiferromagnetic fluctuations is confined to the Ce-BLs, indicating that magnetic degrees of freedom of f-electrons are quenched inside the Yb-BLs. Contrary to simple expectations that the two-dimensionalization enhances fluctuations, we observe that antiferromagnetic fluctuations are rapidly suppressed with decreasing Ce-BL thickness. Moreover, the suppression is more prominent near the interfaces between the BLs. These results imply significant effects of local inversion-symmetry breaking at the interfaces.