Generation of multiple plasmons in strontium niobates mediated by local field effects

TL;DR

This study uses first-principles calculations to explain the experimental observation of multiple plasmons in oxygen-rich strontium niobates, showing how local field effects and oxygen stoichiometry enable tunable plasmon generation in the visible to ultraviolet range.

Contribution

It demonstrates that local field effects are crucial for reproducing multiple plasmons and spectral weight transfer in SrNbO$_{3+\

Findings

Local field effects are essential for multiple plasmon generation.

Plasmons can be tuned by oxygen content and superstructure.

Theoretical results align with experimental observations.

Abstract

Recently, an anomalous generation of multiple plasmons with large spectral weight transfer in the visible to ultraviolet range (energies below the band gap) has been experimentally observed in the insulating-like phase of oxygen-rich strontium niobium oxides (SrNbO$_{3+\delta}$). Here, we investigate the ground state and dielectric properties of SrNbO$_{3+\delta}$ as a function of $\delta$ by means of extensive first principle calculations. We find that in the random phase approximation by taking into account the local field effects (LFEs), our calculations are able to reproduce both the unconventional multiple generations of plasmons and spectral weight transfers, consistent with experimental data. Interestingly, these unconventional plasmons can be tuned by oxygen stoichiometry as well as microscopic superstructure. This unusual predominance of LFEs in this class of materials is ascribed to the strong electronic inhomogeneity and high polarizability and paves a new path to induce multiple plasmons in the untapped visible to ultraviolet ranges of insulating-like oxides.