Figure 4

(a) Low-loss EELS spectra recorded across the Bi₂Se₃/SiO₂ interface ranging from the bulk Bi₂Se₃ at 6 nm (red) to the bulk SiO₂ at − 6 nm (blue) with 0 nm (green) corresponding to the interface. The inset shows a highlight of the \(\pi\) plasmon region with labels 1 to 5 corresponding to the locations marked on the HAADF image. Spectra are offset for clarity. (b) HAADF and spectral maps of the Bi₂Se₃/SiO₂ interface. For the \(\pi\) plasmon, the blue channel corresponds to 6.9–7.9 eV. The green channel corresponds to 5–6 eV. For the \(\pi + \sigma\) plasmon, the cyan channel corresponds to 17–18 eV and the magneta channel corresponds to 22.5–23.5 eV.