Crossover from lattice to plasmonic polarons of a spin-polarised electron gas in ferromagnetic EuO

J M Riley,L Bawden,C Verdi,L B Duffy,F Giustino,K Volckaert,F Caruso,P D C King,G Van Der Laan,M Hoesch,M D Watson,T Hesjedal

doi:10.1038/s41467-018-04749-w

Abstract

Strong many-body interactions in solids yield a host of fascinating and potentially useful physical properties. Here, from angle-resolved photoemission experiments and ab initio many-body calculations, we demonstrate how a strong coupling of conduction electrons with collective plasmon excitations of their own Fermi sea leads to the formation of plasmonic polarons in the doped ferromagnetic semiconductor EuO. We observe how these exhibit a significant tunability with charge carrier doping, leading to a polaronic liquid that is qualitatively distinct from its more conventional lattice-dominated analogue. Our study thus suggests powerful opportunities for tailoring quantum many-body interactions in solids via dilute charge carrier doping.

Highlights

Strong many-body interactions in solids yield a host of fascinating and potentially useful physical properties
We demonstrate in this work that polarons which are formed via a coupling to collective plasmon excitations of an electron gas provide a highly tuneable system
We stress that our findings should not be specific to EuO, but rather a general feature of band insulators where conductivity can be induced by dilute charge carrier doping

Summary

Introduction

Strong many-body interactions in solids yield a host of fascinating and potentially useful physical properties. From angle-resolved photoemission experiments and ab initio many-body calculations, we demonstrate how a strong coupling of conduction electrons with collective plasmon excitations of their own Fermi sea leads to the formation of plasmonic polarons in the doped ferromagnetic semiconductor EuO. We observe how these exhibit a significant tunability with charge carrier doping, leading to a polaronic liquid that is qualitatively distinct from its more conventional lattice-dominated analogue. We demonstrate in this work that polarons which are formed via a coupling to collective plasmon excitations of an electron gas provide a highly tuneable system We investigate this in the doped ferromagnet EuO.

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Conclusion