Temperature dependence of energies and broadening parameters of the band-edge excitons ofReS2andReSe2

We have measured the temperature dependence of the spectral features in the vicinity of the direct gaps ${\mathrm{E}}_{\mathrm{g}}^{\mathrm{d}}$ of ${\mathrm{ReS}}_{2}$ and ${\mathrm{ReSe}}_{2}$ in the temperature range between 25 and 450 K using piezoreflectance (PzR). From a detailed line-shape fit to the PzR spectra we have been able to determine accurately the temperature dependence of the energies and broadening parameters of the band-edge excitons. The parameters that describe the temperature variation of the transition energies and broadening function have been evaluated.