Coherent backscattering in quasi-ballistic ultra-high mobility GaAs/AlGaAs 2DES.

A small and narrow negative-magnetoresistance (MR) effect that appears about null magnetic field over the interval -0.025 ≤ B ≤ 0.025 T in magnetotransport studies of the GaAs/AlGaAs 2D system with μ ≈ 10cm/Vs is experimentally examined as a function of the sample temperature, T. The temperature dependent magnetoresistance data were fit using the Hikami et al. theory, without including the spin-orbit correction, to extract the inelastic length, l, which decreases rapidly with increasing temperature. It turns out that l < l, where l is the elastic length, for all T. Thus, we measured the single particle lifetime, τ, and the single particle mean free path l = vτ. A comparison between l and l indicates that l > l. The results suggest that the observed small and narrow magnetoresistance effect about null magnetic field could be a manifestation of coherent backscattering due to small angle scattering from remote ionized donors in the high mobility GaAs/AlGaAs 2DES.