Figure 6.

Zero-temperature conductivity as a function of the Fermi energy for a rectangular sample with width-to-length ratio $W/L=5$ (solid blue line) and the Corbino disk with radii ratio $R_2/R_1=2$ (dashed red line). Both systems are shown schematically. Dashed black line marks the universal conductivity ${\sigma }_0=(4/\pi )e^2/h$.