The optical properties of tellurium under high pressure

Reflectivity spectra of Te have been measured in the energy range from 0.5 to 3.8 eV at pressures up to 96 kbar using a diamond anvil cell. Optical conductivity spectra sigma ( omega ) have been derived from the reflectivity by using an oscillator fitting analysis. The sigma ( omega ) spectrum for trigonal Te at 1 kbar has a main peak at 2.2 eV and a shoulder around 1.2 eV. These peaks shift to lower energy and grow with increasing pressure. When Te is transformed into a monoclinic phase around 40 kbar, a Drude term appears in the low-energy region of the sigma ( omega ) spectrum, which suggests that monoclinic Te has a metallic nature. In the orthorhombic phase at 73 kbar, a main peak at 0.5 eV and a shoulder around 1.2 eV are observed for the sigma ( omega ) spectrum. These changes in the sigma ( omega ) spectra of Te with pressure are discussed in comparison with the results of band calculations.