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arXiv · 2206.14083

Gapped collective charge excitations and interlayer hopping in cuprate superconductors

M. Hepting·M. Bejas·A. Nag·H. Yamase·N. Coppola·D. Betto·C. Falter·M. Garcia-Fernandez·S. Agrestini·K. -J. Zhou·M. Minola·C. Sacco·L. Maritato·P. Orgiani·H. I. Wei·K. M. Shen·D. G. Schlom·A. Galdi·A. Greco·B. Keimer
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Abstract

We use resonant inelastic x-ray scattering (RIXS) to probe the propagation of plasmons in the electron-doped cuprate superconductor Sr$_{0.9}$La$_{0.1}$CuO$_2$ (SLCO). We detect a plasmon gap of $\sim$~120 meV at the two-dimensional Brillouin zone center, indicating that low-energy plasmons in SLCO are not strictly acoustic. The plasmon dispersion, including the gap, is accurately captured by layered $t$-$J$-$V$ model calculations. A similar analysis performed on recent RIXS data from other cuprates suggests that the plasmon gap is generic and its size is related to the magnitude of the interlayer hopping $t_z$. Our work signifies the three-dimensionality of the charge dynamics in layered cuprates and provides a new method to determine $t_z$.

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M. Hepting, M. Bejas, A. Nag, H. Yamase, N. Coppola, D. Betto, C. Falter, M. Garcia-Fernandez, S. Agrestini, K. -J. Zhou, M. Minola, C. Sacco, L. Maritato, P. Orgiani, H. I. Wei, K. M. Shen, D. G. Schlom, A. Galdi, A. Greco, B. Keimer. 2022-06-28. Gapped collective charge excitations and interlayer hopping in cuprate superconductors. https://doi.org/10.1103/physrevlett.129.047001

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