Optical conductivity and vibrational spectra of the narrow-gap semiconductor FeGa3

The authors perform optical, Raman, and M\"ossbauer spectroscopy measurements of the narrow-gap semiconductor FeGa${}₃$, along with DFT band structure and vibrational frequencies calculation. The results indicate that the spectral weight below the charge gap of approximately 0.4 eV originates from the impurities and not from the correlation effects. Both the infrared and Raman lines are very narrow, and so too are the M\"ossbauer spectral lines, which implies a good crystallinity of the sample.