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 1Ϫx As/GaAs heterostructures with different starting disorders. We demonstrate that the diffusion theory works down to k F lӍ1.5Ϫ2, where k F is the Fermi quasimomentum and l 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.Quantum corrections to the conductivity in disordered metals and doped semiconductors have been intensively studied since 1980. 1 Two mechanisms led to these corrections: ͑i͒ the interference of the electron waves propagating in opposite directions along closed paths; ͑ii͒ electronelectron (e-e) interaction. The interference decreases the conductivity and its role increases with decreasing temperature. Behavior of the e-e contribution to the conductivity strongly depends on value of k B T/ប, where is transport relaxation time, and Fermi liquid interaction parameter F 0 . 2,3 It dramatically changes at crossover from the diffusion regime (k B T/បӶ1) to the ballistic one (k B T/បտ1) and can lead to inversion of sign of the temperature dependence of the conductivity. In addition, in the ballistic regime the e-e contribution depends on scale of scattering potential. The interaction correction for pointlike scattering potential was considered in Refs. 2 and 3 and for the long-range potential was studied theoretically in Ref. 4 and experimentally in Ref. 5. In this paper we track the evolution of the interaction correction as the conductivity decreases. Because the absolute value of both interference and interaction corrections increases with decreasing temperature, they determine in large part the low-temperature transport in two-dimensional ͑2D͒ systems in this case. The interference or weaklocalization ͑WL͒ correction ␦ WL is proportional to Ϫln( /), where is the phase relaxation time, ϰT Ϫp , pӍ1 in dirty limit. The correction due to the e-e interaction ␦ ee is proportional to Ϫln͓ប/(k B T)͔ in the diffusion regime. 1 It immediately follows that at increasing disorder, i.e., at decreasing , both corrections have to be enhanced in absolute value and can become comparable with the Drude conductivity. In this case the low-temperature conductivity will be significantly less than the Drude conductivity, and the strong temperature dependence of the conductivity has to appear. On further increase of disorder the transition to the hopping conductivity has to occur.All theories of quantum corrections for both diffusive 1 and ballistic 2-4 regimes were developed for the case k F l ӷ1, where k F and l are the Fermi quasimomentum and the classical mean free path, respectively. Under this condition the quantum corrections to the conductivity are small in magnitude compared with the Drude conductivity 0 ϭk F lG 0 with G 0 ϭe 2 /(2 2 ប) at any accessible temperature. With decreasing k F l ...

Weak antilocalization is studied in an InGaAs quantum well. Anomalous magnetoresistance is measured and described theoretically in fields perpendicular, tilted and parallel to the quantum well plane. Spin and phase relaxation times are found as functions of temperature and parallel field. It is demonstrated that spin dephasing is due to the Dresselhaus spin-orbit interaction. The values of electron spin splittings and spin relaxation times are found in the wide range of 2D density. Application of in-plane field is shown to destroy weak antilocalization due to competition of Zeeman and microroughness effects. Their relative contributions are separated, and the values of the in-plane electron g-factor and characteristic size of interface imperfections are found.Comment: 8 pages, 8 figure

The results of an experimental study of interaction quantum correction to the conductivity of two-dimensional electron gas in A3B5 semiconductor quantum well heterostructures are presented for a wide range of T τ -parameter (T τ ≃ 0.03 − 0.8), where τ is the transport relaxation time. A comprehensive analysis of the magnetic field and temperature dependences of the resistivity and the conductivity tensor components allows us to separate the ballistic and diffusion parts of the correction. It is shown that the ballistic part renormalizes in the main the electron mobility, whereas the diffusion part contributes to the diagonal and does not to the off-diagonal component of the conductivity tensor. We have experimentally found the values of the Fermi-liquid parameters describing the electron-electron contribution to the transport coefficients, which are found in a good agreement with the theoretical results.

The interaction correction to the conductivity of 2D hole gas in strained GaAs/InxGa1−xAs/GaAs quantum well structures was studied. It is shown that the Zeeman splitting, spin relaxation and ballistic contribution should be taking into account for reliable determination of the Fermi-liquid constant F σ 0 . The proper consideration of these effects allows us to describe both th temperature and magnetic field dependences of the conductivity and find the value of F σ 0 .