is carried out in the Appendix \[appA\]. The result (\[detT\]) shows that $$Z_4(x,y,z)-Z_2(y)Z_2(z)\simeq O\left(c^2(x)\right)
\label{y->infty}$$ for $x\rightarrow\infty$. Hence, the integral in grows faster than $L$ and the function $G(y,z)$ diverges if $c(x)\propto 1/x^n$ with $n < 1/2$ for $x\rightarrow\infty$. We see that for slowly decaying correlation function $c(x)$ the diffusivity does not exist, spreading of the photocurrent transients is anomalous and does not follow the law $\propto t^{1/2}$. For the exactly critical correlation function $c(x)\propto 1/x^{1/2}$ the function $G(y,z)$ is finite and diffusivity does exist but the mER is not valid. In this model the breakdown of the mER is a signal of the emerging development of the anomalous diffusive regime.

It turns out that the superlinear growth of the integral (\[lin\]) is not the only mechanism of the breakdown of the normal diffusive transport (we will call it the mechanism I). Another possibility is the divergence of the correlation function $Z_4(x,y,z)$ for $\varkappa < 1$ (the mechanism II). Let us consider this possibility. We start with the consideration of the particular case of the exponential correlation function $c(x)=\exp(-x/a)$, where all terms $c(x+y)$, $c(y+z+x)$, and $c(z+x)$ could be expressed through $c(x)$, $c(y)$, and $c(z)$ as $c(x+y)=c(x)c(y)$ etc. Result of the 