Plasmon spectrum of single-layer antimonene

The collective excitation spectrum of two-dimensional (2D) antimonene is calculated beyond the low-energy continuum approximation. The dynamical polarizability is computed using a six-orbital tight-binding model that properly accounts for the band structure of antimonene in a broad energy range. Electron-electron interaction is considered within the random phase approximation. The obtained spectrum is rich, containing the standard intraband 2D plasmon and a set of single interband modes. We find that spin-orbit interaction plays a fundamental role in the reconstruction of the excitation spectrum, with the emergence of novel interband branches in the continuum that interact with the plasmon.