Polarization dependence of the fundamental absorption edge and the Urbach rule in PbMoO4 crystals

The fundamental absorption tail of PbMoO4 crystals has been investigated in the ac plane in a wide temperature range between 6 and 300 K by using linearly polarized light. A remarkable dichroism between E//a and E//c is observed in the tail region. A defect-related absorption band is clarified for the polarization E//a. It is found that the Urbach rule holds for the absorption spectra measured with light polarized with E//c. The results of the analysis of the Urbach tail are discussed in comparison with the experimental results on the exciton transition and luminescence properties in this material. (Abstract Copyright [2010], Wiley Periodicals, Inc.)