Giant negative magnetoresistance in high-mobility two-dimensional electron systems

Abstract

We report on a giant negative magnetoresistance in very high mobility GaAs/AlGaAs heterostructures and quantum wells. The effect is the strongest at B ≃ 1 kG, where the magnetoresistivity develops a minimum emerging at T 2 K. Unlike the zero-field resistivity which saturates at T ≃ 2 K, the resistivity at this minimum continues to drop at an accelerated rate to much lower temperatures and becomes several times smaller than the zero-field resistivity. Unexpectedly, we also find that the effect is destroyed not only by increasing temperature but also by modest in-plane magnetic fields. The analysis shows that giant negative magnetoresistance cannot be explained by existing theories considering interaction-induced or disorder-induced corrections.

Nonlinear transport in two-dimensional electron gas exhibiting colossal negative magnetoresistance

“…In the range of magnetic fields corresponding to the resistivity minimum at zero bias, the resistivity increases linearly with current and the rate of this increase scales with the inverse magnetic field. The latter observation is consistent with the theory, proposed more than 35 years ago, considering classical memory effects in the presence of strong, dilute scatterersThe interest to low-field magnetotransport in twodimensional electron systems (2DES) has been recently revived owing to several experiments reporting unexpectedly strong negative magnetoresistance in GaAs/AlGaAs heterostructures [1][2][3][4][5][6][7][8]. One prominent example is the observation of a colossal negative magnetoresistance (CNMR), which is marked by a sharp drop of the resistivity ρ(B) followed by a saturation at the magnetic field…”

“…The interest to low-field magnetotransport in twodimensional electron systems (2DES) has been recently revived owing to several experiments reporting unexpectedly strong negative magnetoresistance in GaAs/AlGaAs heterostructures [1][2][3][4][5][6][7][8]. One prominent example is the observation of a colossal negative magnetoresistance (CNMR), which is marked by a sharp drop of the resistivity ρ(B) followed by a saturation at the magnetic field B ≈ B ⋆ ≈ 1 kG, close to ρ ⋆ ≡ ρ(B ⋆ ) 0.1ρ 0 , at temperature T 1 K [7].…”

Nonequilibrium phenomena in high Landau levels

“…(b) Magneticfield dependence of the resistivity for different temperatures from 0.5 to 1.75 K in steps of 0.25 K in a sample with µ ≃ 5.4 × 10 6 cm 2 /V s and ne ≃ 1.6 × 10 11 cm −2 . Adapted from Hatke et al (2012c). leads to a longer time between collisions with different strong scatterers, hence the negative sign of the MR. This should be contrasted with the positive MR (15) for onescale smooth disorder, where the passages through the same area increase the scattering rate.…”

Nonlinear response in overlapping and separated Landau levels of GaAs quantum wells

“…(3). Finally, we mention a recently reported negative magnetoresistivity effect 55,56 which occurs in the same range of magnetic fields and is strongly temperature dependent. Unfortunately, separating all these contributions does not appear feasible at this point.…”