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

Abstract

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 ≈ 107cm2/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, li, which decreases rapidly with increasing temperature. It turns out that li < le, where le is the elastic length, for all T. Thus, we measured the single particle lifetime, τs, and the single particle mean free path ls = vFτs. A comparison between li and ls indicates that li > ls. 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.

Study of narrow negative magnetoresistance effect in ultra-high mobility GaAs/AlGaAs 2DES under microwave photo-excitation

“…The experimental data were fit using the Hikami 2D WL theory 64 , neglecting the spin orbit scattering term, and also electron-electron interaction effects. Our previous reports reveal the absence of electron-electron interaction effect in these specimens 57,65 . In the presence of spin-orbit interaction one would expect a positive magnetoresistance in these types of device structures, rather than a negative magnetoresistance 51,66 .…”

“…We have previously reported the effect of bath temperature on the inelastic scattering length 65 , where the measurements were taken under dark conditions, i.e. without microwaves.…”

“…In addition to the photo-excited effects, the dark magneto-transport properties including positive magnetoresistance 51,52 , giant negative magnetoresistance [53][54][55][56][57][58][59][60][61] , and narrow negative magnetoresistance effect near zero field have also attracted recent experimental attention. So far as the larger negative giant magneto-resistance is concerned, recent studies have shown remarkable features such as size dependence, tunability with supplemental dc-current, and coexistence with-and separability from-radiation induced magnetoresistance oscillations [59][60][61][62][63][64][65] . One emerging theory suggests that some of the observed features of the larger negative giant magnetoresistance effect could be a signature of a viscous electron liquid in the low magnetic field quasi ballistic transport regime.…”

Influence of Microwave Excitation‐Power on the Narrow Negative Magnetoresistance Effect Around B = 0 T in the Ultra‐High Mobility GaAs/AlGaAs 2DES

“…As far as the dark magnetoresistance properties of high mobility GaAs/AlGaAs 2DES are concerned, our previous reports exhibit two distinct dark MR effects, which are: 1) negative Giant Magnetoresistance (negative‐GMR) effect and 2) narrow negative MR effect around B = 0 T. Experimental studies have shown that the negative‐MR effect around zero magnetic fields is temperature dependent (i.e., T ≥ 1 K) . However, another study reported a temperature (i.e., T ≤ 800 mK) invariance of the narrow negative magnetoresistance effect .…”

“…Low temperature transport studies of high mobility ( μ ≥10 7 cm 2 V −1 s −1 GaAs/AlGaAs two‐dimensional electron systems (2DES) grown by molecular beam epitaxy (MBE) have shown that the transport/elastic scattering length of these device structures can be comparable with the dimensions of the specimens even in the mm scale . Thus, quasi‐ballistic transport is possible in such specimens in the absence of a magnetic field.…”