Electron-electron interaction with decreasing conductance

The contribution of the electron-electron interaction to conductivity is analyzed step by step starting from the high conductivity in gated GaAs/In x Ga 1 - x As/GaAs heterostructures with different starting disorders. We demonstrate that the diffusion theory works down to k F l≃1.5 - 2, where k F is the Fermi quasimomentum and I is the mean free path. It is shown that the e-e interaction gives smaller contribution to the conductivity than the interference independent of the starting disorder, and its role rapidly decreases with decreasing k F l.