Evidence for modification of the electronic density of states by zero-point lattice motion in one dimension: Luminescence and resonance Raman studies of anMXsolid

Luminescence spectra, both emission and excitation, and the excitation dependence of the resonance Raman spectra, have been measured for the quasi-one-dimensional charge-density-wave material [Pt(en${)}_2$][Pt(en${)}_2$ ${\mathrm{Cl}}_2$](${\mathrm{ClO}}_4$ ${)}_4$, en=1,2-diaminoethane. While the luminescence experiments show the existence of tail states at low temperature in the band gap region, the Raman measurements conclusively demonstrate that this tail does not arise from ordinary static structural disorder. These results can be explained by considering the zero-point motion of the lattice.