Optical Study Of The Multiple Charge-Density-Wave Transitions In Erte3

We present an optical spectroscopy study on singe crystalline ErTe3, a rare-earth-element tritelluride, which experiences two successive charge-density wave (CDW) transitions at T-c1 = 267 K and T-c2 = 150 K. Two corresponding gap features, centered at 2770 cm(-1) (similar to 343 meV) and 890 cm(-1) (similar to 110 meV), respectively, are clearly seen in ordered state. A pronounced Drude component, which exists at all measurement temperatures, demonstrates the partial gap character of both CDW orders. About half of the unmodulated Fermi surface (FS) remains in the CDW state at the lowest measurement temperature. The study also indicates that fluctuation effect may be still prominent in this two-dimensional material.