Interplay of Dirac fermions and heavy quasiparticles in solids

TL;DR

This paper explores the coexistence and interaction of Dirac fermions and heavy quasiparticles in solids, demonstrating their mutual influence at surfaces and in the bulk, with implications for understanding complex many-body phenomena.

Contribution

It reveals that Dirac fermions and heavy quasiparticles can coexist and strongly interact within a single solid, a novel insight into correlated electron systems.

Findings

Dirac fermions and heavy quasiparticles coexist in EuRh2Si2

Interactions occur at both surface and bulk levels

Linear dispersion is dictated by crystal symmetry

Abstract

Many-body interactions in crystalline solids can be conveniently described in terms of quasiparticles with strongly renormalized masses as compared to those of non-interacting particles. Examples of extreme mass renormalization are on the one hand graphene, where the charge carriers obey the linear dispersion relation of massless Dirac fermions, and on the other hand heavy-fermion materials where the effective electron mass approaches the mass of a proton. Here we show that both extremes, Dirac fermions like they are found in graphene and extremely-heavy quasiparticles characteristic for Kondo materials, may not only coexist in a solid but can undergo strong mutual interactions. Using the example of EuRh2Si2 we explicitly demonstrate that these interactions can take place at the surface and in the bulk. The presence of the linear dispersion is imposed solely by the crystal symmetry while the existence of heavy quasiparticles is caused by the localized nature of the 4f states.