Raman phonons of $\alpha$-FeTe and Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$ single crystals

TL;DR

This study investigates the Raman phonon spectra of $ ext{FeTe}$ and $ ext{Fe}_{1.03} ext{Se}_{0.3} ext{Te}_{0.7}$ single crystals, identifying phonon modes and exploring differences related to superconductivity and electronic interactions.

Contribution

The paper provides experimental Raman spectra and symmetry-based phonon mode assignments for both compounds, highlighting differences associated with superconductivity and electronic effects.

Findings

Clear A$_{1g}$ and B$_{1g}$ phonon modes in $ ext{FeTe}$

Softened B$_{1g}$ mode in superconducting $ ext{Fe}_{1.03} ext{Se}_{0.3} ext{Te}_{0.7}$

Slight electronic enhancement below 300 cm$^{-1}$ in superconducting sample

Abstract

The polarized Raman scattering spectra of nonsuperconducting $\alpha$-FeTe and of the newly discovered, As-free superconductor Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$ are measured at room temperature on single crystals. The phonon modes are assigned by combining symmetry analysis with first-principles calculations. In the parent compound $\alpha$-FeTe, the A$_{1g}$ mode of the Te atom and the B$_{1g}$ mode of the Fe atom are observed clearly, while in superconducting Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$, only a softened Fe B$_{1g}$ mode can be seen. No electron-phonon coupling feature can be distinguished in the spectra of the two samples. By contrast, the spectra of the superconducting system show a slight enhancement below 300$cm^{-1}$, which may be of electronic origin.