Nonlinear resistance of two-dimensional electrons in crossed electric and magnetic fields

The longitudinal resistivity of two-dimensional (2D) electrons placed in strong magnetic field is significantly reduced by applied electric field, an effect which is studied in a broad range of magnetic fields B and temperatures T in GaAs quantum wells with high electron density. The data are found to be in good agreement with theory, considering the strong nonlinearity of the resistivity as the result of nonuniform spectral diffusion of the 2D electrons. Inelastic processes limit the diffusion. Comparison with the theory yields the inelastic scattering time τᵢₙ of the two-dimensional electrons. In the temperature range T=2--10 K for overlapping Landau levels, the inelastic scattering rate 1/τᵢₙ is found to be proportional to T², indicating a dominant contribution of the electron-electron scattering to the inelastic electron relaxation. In a strong magnetic field, the nonlinear resistivity demonstrates scaling behavior, indicating a specific regime of electron heating of well-separated Landau levels. In this regime the inelastic scattering rate is found to be proportional to T³, suggesting the electron-phonon scattering as the dominant mechanism of the inelastic relaxation. At low temperatures and separated Landau levels an additional regime of the inelastic electron relaxation is observed: τᵢₙ~T^-1.26.