Energy loss spectrum and surface modes of two-dimensional black phosphorus

The structural features and the electron energy loss spectrum of black phosphorus (BP) have been experimentally analyzed and they are discussed based on a theoretical calculation. The low-energy loss spectra of typical samples reveal that the emerging high-mobility two-dimensional material BP often exhibits both bulk and surface plasmon modes. The surface modes of BP are strongly thickness dependent. Electrodynamic analysis indicates that the Fuchs–Kliewer-like surface plasmon modes consist of two branches with different charge symmetry: the upper side and lower side have the same charge polarity as the lower branch and the opposite charge polarity to the upper branch. This study provides fundamental insight into the characteristic nature of BP plasmonics.