  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.
