Optically Active Lattice Vibrations in Bi₂Se₃

The preparation of Bi 2 Se 3 single crystals with low free carrier densities allowed an investigation of the lattice vibrations to be carried out from the reflectivity of cleavage planes at nearly normal incidence of the radiation ( E ⟂ c ). The experimental results can be explained with two classical oscillators, whose eigenfrequencies occur at 92 and 69.5 cm −1 . The static dielectric constant was determined to be 100 ± 10 for E ⟂ c .