Surface phonons in the topological insulators Bi2Se3 and Bi2Te3. (March 2018)

• Record Type: Journal Article
• Authors: Boulares, Ibrahim; Shi, Guangsha; Kioupakis, Emmanouil; Lošťák, Petr; Uher, Ctirad; Merlin, Roberto
• Is Part Of: Solid state communications. Volume 271(2018)
• Page Start: 1
• Page End: 5
• Publication Date: 2018-03
• Subjects: A. Topological insulators -- D. Surface phonons -- E. Raman spectroscopy; Solid state chemistry -- Periodicals; Solid state physics -- Periodicals; Chimie de l'état solide -- Périodiques; Physique de l'état solide -- Périodiques; 530.41
• DOI: 10.1016/j.ssc.2017.12.012
• Languages: English
• ISSNs: 0038-1098

Abstract

Abstract: Raman scattering [K. M. F. Shahil et al., Appl. Phys. Lett. 96, 153103 (2010), V. Gnezdilov et al., Phys. Rev. B 84, 195118 (2011) and H. –H. Kung et al., Phys. Rev. B 95, 245406 (2017)], inelastic helium scattering [X. Zhu et al., Phys. Rev. Lett. 107, 186102 (2011)] and photoemission experiments [J. A. Sobota et al., Phys. Rev. Lett. 113, 157401 (2014)] on the topological insulators Bi2 Se3 and Bi2 Te3 show features in the range ∼ 50–160 cm −1, which have been assigned alternatively to Raman-forbidden, bulk infrared modes arising from symmetry breaking at the surface or to surface phonons, which couple to the topologically protected electronic states. Here, we present temperature- and wavelength- dependent Raman studies showing additional modes we ascribe to surface phonons in both Bi2 Se3 and Bi2 Te3 . Our assignment is supported by density functional theory calculations revealing surface phonons at frequencies close to those of the extra peaks in the Raman data. The theoretical results also indicate that these modes are not a consequence of spin-orbit coupling and, thus, that their occurrence is unrelated to the topological properties of these materials. Highlights: Observation of localized surface modes in Bi2 Se3 and Bi2 Te3 single crystals. DFT surface phonon calculations. Temperature- and excitation-wavelength- dependent Raman data.