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Title: Sharp Raman anomalies and broken adiabaticity at a pressure induced transition from band to topological insulator in Sb 2 Se 3
Authors: Sen, Somaditya
Keywords: Physics
Issue Date: 2013
Publisher: Physical Review Letters
Citation: Physical Review Letters, vol. 110, no. 10, Mar. 2013
Series/Report no.: JA08;
Abstract: The nontrivial electronic topology of a topological insulator is thus far known to display signatures in a robust metallic state at the surface. Here, we establish vibrational anomalies in Raman spectra of the bulk that signify changes in electronic topology: an E2 g phonon softens unusually and its linewidth exhibits an asymmetric peak at the pressure induced electronic topological transition (ETT) in Sb2Se3 crystal. Our first-principles calculations confirm the electronic transition from band to topological insulating state with reversal of parity of electronic bands passing through a metallic state at the ETT, but do not capture the phonon anomalies which involve breakdown of adiabatic approximation due to strongly coupled dynamics of phonons and electrons. Treating this within a four-band model of topological insulators, we elucidate how nonadiabatic renormalization of phonons constitutes readily measurable bulk signatures of an ETT, which will facilitate efforts to develop topological insulators by modifying a band insulator.
Appears in Collections:Discipline of Physics

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