Tunable Collective Excitations in Epitaxial Perovskite Nickelates

TL;DR

This study investigates how orbital hybridization influences plasmonic excitations in epitaxial La1-xSrxNiO3 films, revealing that enhanced hybridization suppresses correlated plasmons at certain doping levels, with implications for optoelectronic applications.

Contribution

It provides new insights into the role of orbital hybridization and doping in controlling plasmonic behavior in nickelate films, highlighting their potential for device applications.

Findings

Correlated plasmons are absent at intermediate doping (x=0.125) despite high optical conductivity.

Enhanced O2p-Ni3d hybridization correlates with suppression of correlated plasmons.

Orbital hybridization significantly impacts plasmon formation in strongly-correlated systems.

Abstract

The formation of plasmons through the collective excitation of charge density has generated intense discussions, offering insights to fundamental sciences and potential applications. While the underlying physical principles have been well-established, the effects of many-body interactions and orbital hybridization on plasmonic dynamics remain understudied. In this work, we present the observation of conventional metallic and correlated plasmons in epitaxial La1-xSrxNiO3 (LSNO) films with varying Sr doping concentrations (x = 0, 0.125, 0.25), unveiling their intriguing evolution. Unlike samples at other doping concentrations, the x = 0.125 intermediate doping sample does not exhibit the correlated plasmons despite showing high optical conductivity. Through a comprehensive experimental investigation using spectroscopic ellipsometry and X-ray absorption spectroscopy, the O2p-Ni3d orbital hybridization for LSNO with a doping concentration of x = 0.125 is found to be significantly enhanced, alongside a considerable weakening of its effective correlation U*. These factors account for the absence of correlated plasmons and the high optical conductivity observed in LSNO (0.125). Our results underscore the profound impact of orbital hybridization on the electronic structure and the formation of plasmon in strongly-correlated systems. This in turn suggest that LSNO could serve as a promising alternative material in optoelectronic devices.