Recently, electron correlation has been shown to play an important role in unconventional plasmon generation in highly correlated electron systems. Electrons in topological insulators, on the other hand, are massless and insensitive to nonmagnetic scattering due to their protection by time-reversal symmetry, which makes these materials appealing platforms for hosting exotic plasmonic excitations. Here, using a combination of angle-dependent spectroscopic ellipsometry and angle-resolved photoemission spectroscopy as a function of temperature supported by first-principles calculations, we reveal a new pair of correlated plasmonic excitations at 1.04 and 1.52 eV and a significant Fermi level shift of 0.12 eV accompanied by spectral weight transfer in the topological insulator bismuth selenide (Bi₂Se₃). Interestingly, such a spectral weight transfer over a broad energy range causes a drastic change in the charge carrier density whereby the contribution of charge carriers in the bulk starts to rival those in the surface states and Bi₂Se₃ becomes more uniformly conducting. Our results show the importance of electronic correlations in determining the electronic structure and appearance of correlated plasmons in topological insulators and their potential applications in plasmonics.

近来，已经证明电子相关在高度相关的电子系统中的非常规等离子体激元产生中起重要作用。另一方面，由于拓扑绝缘体中的电子受到时间反转对称性的保护，因此它们是无质量的并且对非磁性散射不敏感，这使这些材料吸引了用于承载外来等离子体激元的平台。在这里，结合角度相关光谱椭圆仪和角度分辨光发射光谱法作为第一原理计算所支持的温度的函数，我们揭示了一对新的相关等离子体激元在1.04和1.52 eV的对以及费米能级显着的变化。 0.12 eV伴随着光谱绝缘体中的硒化铋（Bi ₂ Se ₃）。有趣的是，这种在较宽的能量范围内的光谱重量转移导致电荷载流子密度的急剧变化，由此，大部分中的电荷载流子的贡献开始与表面态的电荷载流子的竞争相抗，并且Bi ₂ Se ₃变得更均匀地导电。我们的结果表明，电子相关性对于确定拓扑绝缘子中相关等离激元的电子结构和外观及其在等离激元中的潜在应用至关重要。