Infrared spectroscopy of a novel iron-based superconductor Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$

We will present the results of our infrared and optical studies of a novel iron-based superconductor Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$ with T$_c$ = 8 K. Measurements have been performed over a broad range of frequencies (50 - 50,000 cm$^{-1}$) and temperatures (10 - 300 K). Our results reveal that the superconducting state develops from an unconventional normal state, without well defined quasiparticles. The structural and magnetic phase transitions at T$\simeq$~23~K do not seem to have significant effect on optical properties of Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$. We introduce ``generalized spectral weight'' analysis, and use it to track the redistribution of spectral weigh with temperature.