Plasmon and interband transitions inTi1−xHfxSe2systems

Thermoreflectance measurements in the infrared were performed to study plasmon and low-energy interband transitions both below and above $T_c$ in ${\mathrm{Ti}}_{1-x}{\mathrm{Hf}}_x{\mathrm{Se}}_2$ crystals. We found that the main effect of the introduction of Hf into Ti${\mathrm{Se}}_2$ is to broaden the plasmon structure. Furthermore, through a detailed analysis of a low-energy interband transition, we followed the progressive uncrossing of the bands and estimated the value of the gap opened by the phase transition.