Colossal negative magnetoresistance in a two-dimensional electron gas

Abstract

We report on a colossal negative magnetoresistance (MR) in GaAs/AlGaAs quantum well which, at low temperatures, is manifested by a drop of the resistivity by more than an order of magnitude at a magnetic field B ≈ 1 kG. In contrast to MR effects discussed earlier, the MR reported here is not parabolic, even at small B, and persists to much higher in-plane magnetic fields and temperatures. Remarkably, the temperature dependence of the resistivity at B ≈ 1 kG is linear over the entire temperature range studied (from 1 to 30 K) and appears to coincide with the high-temperature limit of the zero-field resistivity, hinting on the important role of acoustic phonons.

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…”

“…In this Rapid Communication we report on nonlinear transport measurements in a Hall bar-shaped 2DES exhibiting CNMR, marked by ρ ⋆ ∼ 0.1ρ 0 at B ⋆ ≃ 1 kG [7], over a wide range of B and direct currents I. While the differential resistivity exhibits at least two distinct types of extrema, which both move to higher B with increasing I, none of them can be described by Eq.…”

“…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]. While classical memory effects due to a unique disorder landscape appear to be the most likely origin of the observed CNMR, comparison with existing theories [9][10][11] revealed huge discrepancy in the characteristic B range where the effect is expected to occur.…”

“…1 we present the differential resistivity r(B) measured at T = 1.5 K under different I from 0 to 350 µA, in steps of 50 µA. At zero current, r(B) ≡ ρ(B) exhibits CNMR [7], which is marked by a sharp drop of the resistivity terminating at ρ ⋆ ≡ ρ(B ⋆ ) ≈ 0.1ρ 0 , where B ⋆ ≈ 1 kG. Under applied current, a local minimum develops in r(B) at B = 0 as the "zero-B peak" splits into two.…”

“…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].…”