Electron-plasmon interaction induced plasmonic-polaron band replication in epitaxial perovskite SrIrO$_3$ films

TL;DR

This paper reports the direct observation of electron-plasmon coupling in epitaxial SrIrO₃ films, revealing plasmonic-polaron bands through advanced photoemission spectroscopy, advancing understanding of many-body interactions in 5d electron systems.

Contribution

It provides the first direct experimental evidence of electron-plasmon interactions causing band replicas in epitaxial SrIrO₃, highlighting their importance in quasiparticle dynamics.

Findings

Observation of plasmonic-polaron replica bands in SrIrO₃

Electron-plasmon coupling influences quasiparticle behavior

Demonstration of electron-plasmon interactions in 5d systems

Abstract

Electron-boson interaction is fundamental to a thorough understanding of various exotic properties emerging in many-body physics. In photoemission spectroscopy, photoelectron emission due to photon absorption would trigger diverse collective excitations in solids, including the emergence of phonons, magnons, electron-hole pairs, and plasmons, which naturally provides a reliable pathway to study electron-boson couplings. While fingerprints of electron-phonon/-magnon interactions in this state-of-the-art technique have been well investigated, much less is known about electron-plasmon coupling, and direct observation of the band renormalization solely due to electron-plasmon interactions is extremely challenging. Here by utilizing integrated oxide molecular-beam epitaxy and angle-resolved photoemission spectroscopy, we discover the long sought-after pure electron-plasmon coupling-induced low-lying plasmonic-polaron replica bands in epitaxial semimetallic SrIrO$_3$ films, in which the characteristic low carrier concentration and narrow bandwidth combine to provide a unique platform where the electron-plasmon interaction can be investigated kinematically in photoemission spectroscopy. This finding enriches the forms of electron band normalization on collective modes in solids and demonstrates that, to obtain a complete understanding of the quasiparticle dynamics in 5d electron systems, the electron-plasmon interaction should be considered on equal footing with the acknowledged electron-electron interaction and spin-orbit coupling.