Electronic and Vibrational Excitations on the Surface of the Three-Dimensional Topological Insulator Bi_2Te_3-xSe_x (x = 0, 2, 3)

We study surface states in the three-dimensional topological insulators Bi_2Te_3-xSe_x (x = 0, 2, 3) by polarization resolved resonant Raman spectroscopy. By tracking the spectral intensity of the surface phonon modes with respect to the incident photon energy, we show that the surface phonons are qualitatively similar to their bulk counterparts. Using the resonant Raman excitation profile, we estimated the binding energy of the surface conduction bands relative to bulk conduction bands. In addition, we selectively excite the surface-to-bulk electronic continuum near the Fermi energy in Bi_2Se_3 to determine the strength of Fano interaction between the most prominent surface phonon and the surface-to-bulk continuum.