| Raman phonons of $\alpha$-FeTe and Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$ single crystals (2008) | |||||||||
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| Polarized Raman scattering spectra of nonsuperconducting $\alpha$-FeTe and newly discovered superconducting Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$ single crystals are measured at room temperature. Phonon modes are assigned in combination with symmetry analysis and first-principle calculations. In parent compound $\alpha$-FeTe, A$_{1g}$ mode of Te atom and B$_{1g}$ mode of Fe atom are observed clearly, located at 159.1 and 196.3 $cm^{-1}$, respectively. While in superconducting Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$, A$_{1g}$ mode of Te atom smears out and only B$_{1g}$ mode of Fe atom can be seen. It can be understood as the effect of replacement of Te atoms by Se atoms, which in fact destructs the periodic potential formed by Te atoms. Consequently, B$_{1g}$ mode is shifted to lower frequency 187.8 $cm^{-1}$ compared to parent compound $\alpha$-FeTe. In the spectra of two samples, no electron-phonon coupling feature can be distinguished. And for the superconducting Fe$_{1.03}$Se$_{0.3}$Te$_{0.7}$, Raman spectra below 300 $cm^{-1}$ show a slight enhancement, which may be originated from electronic Raman scattering. It is also found that $\alpha$-FeTe is not quite stable in air. One of the decomposition substances is amorphous Te, which is confirmed on the crystal surfaces irradiated continuously by laser for about 3 hours in vacuum environment.. Comment: 4 pages, 2 tables, 3 figures | |||||||||
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