Revealing the Heavy Quasiparticles in the Heavy-Fermion Superconductor CeCu2Si2

TL;DR

This study uses angle-resolved photoemission spectroscopy to elucidate the quasiparticle dispersion and Fermi surface in CeCu2Si2, revealing the crucial role of Ce 4f electrons and band-dependent hybridization in its heavy fermion behavior and superconductivity.

Contribution

It provides the first detailed experimental mapping of the Fermi surface and quasiparticle dispersion in CeCu2Si2, emphasizing the importance of Ce 4f electrons and local correlations.

Findings

Heavy quasi-two-dimensional electron band near the X point

Moderately heavy three-dimensional hole pockets near the Z point

Strong local correlation effects revealed by comparison with theory

Abstract

The superconducting order parameter of the first heavy-fermion superconductor CeCu2Si2 is currently under debate. A key ingredient to understand its superconductivity and physical properties is the quasiparticle dispersion and Fermi surface, which remains elusive experimentally. Here we present measurements from angle-resolved photoemission spectroscopy. Our results emphasize the key role played by the Ce 4f electrons for the low-temperature Fermi surface, highlighting a band-dependent conduction-f electron hybridization. In particular, we find a very heavy quasi-two-dimensional electron band near the bulk X point and moderately heavy three-dimensional hole pockets near the Z point. Comparison with theoretical calculations reveals the strong local correlation in this compound, calling for further theoretical studies. Our results provide the electronic basis to understand the heavy fermion behavior and superconductivity; implications for the enigmatic superconductivity of this compound are also discussed.