Critical Behavior of Density of States in Disordered System with Localized Electrons

The Coulomb gap in the density of states (DOS) of localized electrons is studied at different magnitudes of an external disorder $A$. Computer modeling has been done to find the DOS at the chemical potential $G_F$ as a function of temperature and $A$. At a given filling factor all curves $G_F\mathrm{}\left(T\right)\mathrm{}$ obtained at different values of $A$ and even from different distribution functions of the external disorder cross each other at one temperature $T_c$. We show that $G_F$ obeys an equation with a fixed point. At this point the subsystem of electrons with energies close to the chemical potential becomes incompressible. A weak singularity of thermodynamic functions at $T=T_c$ is predicted and found by modeling.