Optical phonons are employed to probe a structural phase transition of IrTe2-xSex at TC ∼ 280 K for x = 0 and TC ∼ 491 K for x = 0.45, which is dictated by Ir dimerization with charge modulations. Phonon Raman spectra show a discontinuous change at TC and thermal hysteresis. A165 cm-1 Ag mode involving out-of-plane motions of Te atoms is mostly affected by Se doping. This highlights the role of interlayer Te-Te interactions in inducing the structural instability. For temperatures below TC both x = 0 and x = 0.45 compounds exhibit commonly five zone-folded peaks for the 128 cm-1. Eg in-plane mode and six zone-folded peaks for the 165 cm-1. Ag mode. This is taken as a signature of a respective quintupling and sextupling of the unit cell. Our results, on the one hand, are consistent with a 1/5 charge modulation reported by previous studies and, on the other hand, indicate that the ground state of IrTe2-xSex lies in proximity to a 1/6 commensurate charge modulation phase.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- charge density wave
- structural phase transition