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arXiv · 2502.03779

Out-of-phase Plasmon Excitations in the Trilayer Cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$

S. Nakata·M. Bejas·J. Okamoto·K. Yamamoto·D. Shiga·R. Takahashi·H. Y. Huang·H. Kumigashira·H. Wadati·J. Miyawaki·S. Ishida·H. Eisaki·A. Fujimori·A. Greco·H. Yamase·D. J. Huang·H. Suzuki
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Abstract

Within a homologous series of cuprate superconductors, variations in the stacking of CuO$_2$ layers influence the collective charge dynamics through the long-range Coulomb interactions. We use O $K$-edge resonant inelastic x-ray scattering to reveal plasmon excitations in the optimally-doped trilayer Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$. The observed plasmon exhibits nearly $q_z$-independent dispersion and a large excitation gap of approximately 300 meV. This mode is primarily ascribed to the $\omega_{-}$ mode, where the charge density on the outer CuO$_2$ sheets oscillates out of phase while the density in the inner sheet remains unaltered at $q_z=0$. The intensity of the acoustic $\omega_3$ mode is relatively weak and becomes vanishingly small near $(q_x, q_y)=(0, 0)$. This result highlights a qualitative change in the eigenmode of the dominant low-energy plasmon with the number of CuO$_2$ layers.

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S. Nakata, M. Bejas, J. Okamoto, K. Yamamoto, D. Shiga, R. Takahashi, H. Y. Huang, H. Kumigashira, H. Wadati, J. Miyawaki, S. Ishida, H. Eisaki, A. Fujimori, A. Greco, H. Yamase, D. J. Huang, H. Suzuki. 2025-02-06. Out-of-phase Plasmon Excitations in the Trilayer Cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$. https://doi.org/10.1103/physrevb.111.165141

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