Carrier relaxation time divergence in single and double layer cuprates

We report the transient optical pump-probe reflectivity measurements on single and double layer cuprate single crystals and thin films of ten different stoichiometries. We find that with sufficiently low fluence the relaxation time (<InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\tau_{R})$</EquationSource> </InlineEquation> of all samples exhibits a power law divergence with temperature <InlineEquation ID="Equ2"> <EquationSource Format="TEX">$(T): \tau_{R} \propto T^{-3 \pm 0.5}$</EquationSource> </InlineEquation>. Further, the divergence has an onset temperature above the superconducting transition temperature for all superconducting samples. Possible causes of this divergence are discussed. Copyright Springer-Verlag Berlin/Heidelberg 2003