Quantum Hall effect in the absence of edge currents

Measurements of the Hall conductivity ${\mathrm{\sigma }}_{\mathit{x}\mathit{y}}$ on samples of the Corbino geometry at integer and fractional (i=2/3) filling factors have been carried out. Two different techniques of measurements based on the Laughlin and Widom-Clark ‘‘gedanken’’ experiments were realized. The limits of the two experimental techniques connected with their particularities and the breakdown of the quantum Hall effect are presented. We have also investigated the charge transfer under the conditions of inhomogeneous electron density.