1305.1671 (Colin Howard et al.)

Anomalous behavior in the phonon dispersion of the (001) surface of
Bi$_2$Te$_3$ determined from helium atom-surface scattering measurements    [PDF]

Colin Howard, M. El-Batanouny, R. Sankar, F. C. Chou

We employ inelastic helium atom-surface scattering to measure the low energy phonon dispersion along high-symmetry directions on the surface of the topological insulator Bi$_2$Te$_3$. Results indicate that one particular low-frequency branch experiences noticeable mode softening attributable to the interaction between Dirac fermion quasiparticles and phonons on the surface. This mode softening constitutes a renormalization of the real part of the phonon self-energy. We obtain the imaginary part, and hence lifetime information, via a Hilbert transform. In doing so we are able to calculate an average branch specific electron-phonon coupling constant $<\lambda_\nu> = 1.44$.

View original: http://arxiv.org/abs/1305.1671