Phonon spectrum and bonding properties of Bi2Se3: Role of strong spin-orbit interaction

Phonon dispersions of one typical three-dimensional topological insulator Bi2Se3 have been studied within density functional theory. The soft modes of two acoustic branches along the Z - F and Gamma F directions within the pure local density approximation will transit to show imaginary frequency oscillating after including the spin-orbit interaction (SOI). Similar phenomenon has also been observed for Bi2Te3. Besides, we have found that the weak van der Waals forces between two Se1 layers in Bi2Se3 are strengthened by turning on the spin-orbit interaction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3689759]