Tunneling limit of heavy-fermion point contacts

TL;DR

This paper models tunneling spectra in heavy-fermion superconductors, revealing how low transparency junctions produce BCS-like conductance and explaining experimental asymmetries and suppressed Andreev reflection.

Contribution

It introduces a multichannel tunneling model for heavy-fermion systems, specifically addressing low transparency junctions and their spectral features.

Findings

Low transparency leads to BCS-like tunneling spectra.

Asymmetries in dI/dV are explained by multichannel effects.

Suppressed Andreev reflection is characteristic of heavy-fermion junctions.

Abstract

We present results for a multichannel tunneling model that describes point-contact spectra between a metallic tip and a superconducting heavy-fermion system. We calculate tunneling spectra both in the normal and superconducting state. In point-contact and scanning tunneling spectroscopy many heavy-fermion materials, like CeCoIn5, exhibit an asymmetric differential conductance, dI/dV, combined with a strongly suppressed Andreev reflection signal in the superconducting state. For Andreev reflection to occur a junction has to be in the highly transparent limit. Here we focus on the opposite limit, namely that of low transparency leading to BCS-like dI/dV curves. We discuss the consequences of a multichannel tunneling model for CeCoIn5 assuming itinerant electron bands and localized f electrons.