Evidence for a universal length scale of dynamic charge inhomogeneity in   cuprate superconductors
  Time-resolved optical experiments can give unique information on the characteristic length scales of dynamic charge inhomogeneity on femtosecond timescales. From data on the effective quasiparticle relaxation time &#61556;r in La2-xSrxCuO4 and Nd2-xCexCuO4 we derive the temperature- and doping- dependence of the intrinsic phonon escape length le, which, under certain circumstances, can be shown to be a direct measure of charge inhomogeneity. Remarkably, a common feature of both p and n-type cuprates - which has important consequences for superconductivity - is that as T &#61614; Tc from above, the escape length approaches the zero-temperature superconducting coherence length, le &#61614; &#61560;s(0). In close vicinity of Tc, le appears to follow the critical behaviour of the Ginsburg-Landau coherence length, &#61560;GL(T). In the normal state le is found to be in excellent agreement with the mean free path lm obtained from the resistivity data. The data on le also agree well with the data on structural coherence lengths ls obtained from neutron scattering experiments, implying the existence of complex intrinsic textures on different length scales which may have a profound effect on the functional properties of these materials. 
D.Mihailovic