Charge Ordering in Amorphous WO$_{x}$ Films
We report on the observation of highly anisotropic viscous electronic conducting phase in amorphous WO$_{1.55}$ films that occurs below a current (I)- and frequency (f)- dependent temperature T*(I, f). At T < T*(I, f) the rotational symmetry of randomly disordered electronic background is broken leading to the appearance of mutually perpendicular metallic- and insulating-like states. A rich dynamic behavior of the electronic matter occurring at T < T*(I, f) provides evidence for an interplay between pinning effects and electron-electron interactions. The results strongly suggest a dynamic crystallization of the disordered electronic matter, viz. formation of sliding Wigner crystal, as well as the occurrence of quantum smectic or stripe phase in the pinning-dominated regime.