Optical properties of the charge-density-wave compoundCeTe2

The temperature dependence of the optical conductivity of ${\text{CeTe}}_{2}$ was obtained for the $E\ensuremath{\parallel}ab$ plane and $E\ensuremath{\parallel}c$ axis at photon energies ranging from terahertz to visible light. Two gap states are found in the optical conductivity spectra. The magnitudes of the gaps are estimated to be 0.448 and 0.109 eV in the $E\ensuremath{\parallel}ab$ plane. The former is due to perfect nesting, while the latter is due to imperfect nesting. The magnitude of the gap due to perfect nesting on the $c$ axis is evaluated to be 0.854 eV. The Drude response caused by the ungapped Fermi surface is found only on the $E\ensuremath{\parallel}ab$ plane since ${\text{CeTe}}_{2}$ is a quasi-two-dimensional material. The portion of the ungapped Fermi surface across all Fermi surfaces is about 3%.