L. Santos

Publications (2)14.74 Total impact

• Article: Electron-phonon coupling on the surface of the topological insulator Bi2Se3 determined from surface-phonon dispersion measurements.

  Xuetao Zhu, L Santos, C Howard, R Sankar, F C Chou, C Chamon, M El-Batanouny
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  ABSTRACT: In this Letter, we report measurements of the coupling between Dirac fermion quasiparticles (DFQs) and phonons on the (001) surface of the strong topological insulator Bi2Se3. While most contemporary investigations of this coupling have involved examining the temperature dependence of the DFQ self-energy via angle-resolved photoemission spectroscopy measurements, we employ inelastic helium-atom scattering to explore, for the first time, this coupling from the phonon perspective. Using a Hilbert transform, we are able to obtain the imaginary part of the phonon self-energy associated with a dispersive surface-phonon branch identified in our previous work [Phys. Rev. Lett. 107, 186102 (2011)] as having strong interactions with the DFQs. From this imaginary part of the self-energy we obtain a branch-specific electron-phonon coupling constant of 0.43, which is stronger than the values reported from the angle-resolved photoemission spectroscopy measurements.
  Physical Review Letters 05/2012; 108(18):185501. · 7.37 Impact Factor
• Source

  Available from: Raman Sankar

  Article: Interaction of phonons and dirac fermions on the surface of Bi2Se3: a strong Kohn anomaly.

  Xuetao Zhu, L Santos, R Sankar, S Chikara, C Howard, F C Chou, C Chamon, M El-Batanouny
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  ABSTRACT: We report the first measurements of phonon dispersion curves on the (001) surface of the strong three-dimensional topological insulator Bi2Se3. The surface phonon measurements were carried out with the aid of coherent helium beam surface scattering techniques. The results reveal a prominent signature of the exotic metallic Dirac fermion quasiparticles, including a strong Kohn anomaly. The signature is manifest in a low energy isotropic convex dispersive surface phonon branch with a frequency maximum of 1.8 THz and having a V-shaped minimum at approximately 2kF that defines the Kohn anomaly. Theoretical analysis attributes this dispersive profile to the renormalization of the surface phonon excitations by the surface Dirac fermions. The contribution of the Dirac fermions to this renormalization is derived in terms of a Coulomb-type perturbation model.
  Physical Review Letters 10/2011; 107(18):186102. · 7.37 Impact Factor