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arXiv · 2511.20776

Strong-coupling theory of bilayer plasmon excitations

Hiroyuki Yamase·Luciano Zinni·Matías Bejas·Andrés Greco
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Abstract

Recently plasmon excitations in bilayer lattice systems were studied extensively in the weak-coupling regime. Unlike single-layer systems, these bilayers exhibit two distinct modes, $ω_{\pm}$, which show characteristic dependences upon the momentum and hopping integrals along the $z$ direction. To apply them to cuprates, strong correlation effects should be considered, but a comprehensive analysis has not yet been investigated. In this work, we present a strong-coupling theory to analyze the charge dynamics of a bilayer system, utilizing the $t$-$J$-$V$ model, which includes the long-range Coulomb interaction, $V$, on a lattice. Although our theoretical framework is fundamentally different from the weak-coupling approach, we find that resulting plasmon excitations are similar to those of a weak-coupling theory. A key distinction is that our strong-coupling framework reveals a noticeable suppression of particle-hole excitations, which allows the plasmon modes to remain well-defined over a wider region of momentum. We suggest that the experimentally reported plasmon excitations in Y-based cuprates can be described by the $ω_{-}$ mode, although we call for more systematic experiments to verify this.

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Hiroyuki Yamase, Luciano Zinni, Matías Bejas, Andrés Greco. 2026-01-19. Strong-coupling theory of bilayer plasmon excitations. https://doi.org/10.1103/c6qd-b9by

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