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  Golias, E.; Sánchez-Barriga, J.: Observation of antiphase coherent phonons in the warped Dirac cone of Bi₂Te₃. Physical Review B 94 (2016), p. 161113 (R)/1-5

10.1103/PhysRevB.94.161113
Open Access Version

Abstract:
In this Rapid Communication we investigate the coupling between excited electrons and phonons in the highly anisotropic electronic structure of the prototypical topological insulator Bi2Te3. Using time- and angle-resolved photoemission spectroscopy we are able to identify the emergence and ultrafast temporal evolution of the longitudinal-optical A1g coherent-phonon mode in Bi2Te3. We observe an antiphase behavior in the onset of the coherent-phonon oscillations between the ΓK and the ΓM high-symmetry directions that is consistent with warping. The qualitative agreement between our density-functional theory calculations and the experimental results reveals the critical role of the anisotropic coupling between Dirac fermions and phonon modes in the topological insulator Bi2Te3.