Electron-phonon coupling in epitaxial silicene: scanning tunnelling microscopy and Raman studies

Silicene, which is single layer of silicon atoms packed in a honeycomb structure, has attracted enormous interest due to its Dirac fermion characteristics and a wide range of promising applications. Epitaxial silicene demonstrates a strong interaction with the substrate that dramatically affects its electronic structure. We report that the special coupling between Dirac fermion and lattice vibrations, in other words, electron-phonon coupling (EPC), in silicene layers on Ag(111) surface was probed by in-situ Raman spectroscopy. We find the EPC is significantly modulated due to tensile strain, which results from the lattice mismatch between silicene and the substrate, and the charge doping from the substrate. The special phonon modes corresponding to two-dimensional electron gas scattering at edge sites in the silicene were identified. Detecting relationship between EPC and Dirac fermion through the Raman scattering will provide a direct route to investigate the exotic property in buckled two dimensional honeycomb materials.