Origin of quasilocal plasmons in Nb-substituted EuTiO3

Abstract

Doped perovskite oxides are promising "material building blocks" for achieving tunable and intrinsically low-loss plasmonic features in the visible- to near-infrared range, which are unlikely to obtain from conventional plasmonic materials. Here, using a combination of spectroscopic ellipsometry, soft x-ray absorption, x-ray photoemission, and ultraviolet photoemission spectroscopic measurements we observe an unconventional tunable low-loss quasilocal plasmon in the IR energy (<1 eV) range in the Nb-substituted perovskite oxide EuTiO3 (EuTi1-xNbxO3). This low-loss plasmon oscillation is formed by many-body interactions, an interplay of quasifree d1 electrons and hybridizations of Eu 4f-Ti 3d and O 2p-Ti 3d. We find that the Nb substitution at Ti site modifies the TiO6 octahedral tilting and, consequently, alters the electronic structure. Our study reveals the importance of charge, orbital, and lattice to generate plasmons in EuTi1-xNbxO3. © 2019 American Physical Society.