Abstract:We examine the microwave frequency(f)-variation of the angular-phase-shift, θ 0 , observed in the polarization-angle-dependence of the microwave-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs two-dimensional electron system. By fitting the diagonal resistance R xx vs. θ plots to an empirical cosine square law, we extract the θ 0 and trace its quasi-continuous variation with f. The results suggest that the overall average of θ 0 extracted from Hall bar device sections
“… 24 , 27 . The radiation-induced magnetoresistance oscillations, can be observed roughly over the interval −0.2 ≤ B ≤ 0.2 T (red-curve) 1 , 3 , 5 – 12 , 14 , 15 , 18 , 20 , 24 , 27 – 30 , 32 – 34 , 36 , 39 . Figure 1 Radiation induced magnetoresistance oscillations in R xx in a GaAs/AlGaAs heterostructure 2D electron system.…”
Section: Resultsmentioning
confidence: 99%
“…Such high quality material has demonstrated new 2D physical phenomena such as the photo-excited zero-resistance states 1 , 2 and 1/4− cycle shifted magnetoresistance oscillations 3 induced by low energy photons in the low magnetic field, high filling factor limit. Associated results have produced new interest in the experimental 1 – 39 and theoretical 40 – 62 study of photo-excited transport in low dimensional systems. The dark properties of the GaAs/AlGaAs 2D material system in the low magnetic field limit have also attracted recent experimental attention as the results have helped to provide new insights into both an observable giant magnetoresistance in the 2DES, and a small, narrow negative magnetoresistance near null magnetic field 63 – 77 .…”
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.
“… 24 , 27 . The radiation-induced magnetoresistance oscillations, can be observed roughly over the interval −0.2 ≤ B ≤ 0.2 T (red-curve) 1 , 3 , 5 – 12 , 14 , 15 , 18 , 20 , 24 , 27 – 30 , 32 – 34 , 36 , 39 . Figure 1 Radiation induced magnetoresistance oscillations in R xx in a GaAs/AlGaAs heterostructure 2D electron system.…”
Section: Resultsmentioning
confidence: 99%
“…Such high quality material has demonstrated new 2D physical phenomena such as the photo-excited zero-resistance states 1 , 2 and 1/4− cycle shifted magnetoresistance oscillations 3 induced by low energy photons in the low magnetic field, high filling factor limit. Associated results have produced new interest in the experimental 1 – 39 and theoretical 40 – 62 study of photo-excited transport in low dimensional systems. The dark properties of the GaAs/AlGaAs 2D material system in the low magnetic field limit have also attracted recent experimental attention as the results have helped to provide new insights into both an observable giant magnetoresistance in the 2DES, and a small, narrow negative magnetoresistance near null magnetic field 63 – 77 .…”
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.
“…The novel physical phenomena include both photo‐excited magneto transport effects and dark transport effects. Recent experimental and theoretical studies of high mobility GaAs/AlGaAs 2DES under low energy photo excitation, has demonstrated interesting novel photo‐excited magneto‐transport effects such as zero resistance states and associated radiation induced magnetoresistance oscillations. On the other hand, dark magnetoresistance properties, such as negative‐MR effects exhibited by high‐mobility samples, have also attracted experimental and theoretical interest among the researchers aiming to further understand the transport mechanism in these specimens …”
In addition to the photo-excited zero-resistance states and radiation-induced magnetoresistance oscillations, which can be observed in the high-quality GaAs/AlGaAs two-dimensional electron system (2DES), magnetotransport studies of this 2DES also exhibit interesting dark magnetoresistance effects. Here, a narrow negative magnetoresistance (MR) effect that appears around zero field, and spans over about À0.02 T B 0.02 T is examined. This experimental work aims to study the influence of microwave (MW) photoexcitation on this narrow negative-MR effect in high-mobility GaAs/AlGaAs 2DES. Experimental data exhibit that the observed negative magnetoresistance effect disappears with increasing MW power. For example, the change in magnetoresistance (ΔR xx ) due to the narrow negative-MR effect drops by %50% upon increasing the source power up to about 8 mW. Further analysis shows that the zero-field resistance monotonically increases with increasing the power, suggesting that electron heating due to the energy absorbed from the radiation field accounts for the observed quenching of the narrow negative-MR effect.
Radiation-induced magnetoresistance oscillations are examined in the GaAs/AlGaAs 2D system in the regime where an observed concurrent giant magnetoresistance is systematically varied with a supplementary dc-current, I
dc. The I
dc tuned giant magnetoresistance is subsequently separated from the photo-excited oscillatory resistance using a multi-conduction model in order to examine the interplay between the two effects. The results show that the invoked multiconduction model describes the observed giant magnetoresistance effect even in the presence of radiation-induced magnetoresistance oscillations, the magnetoresistance oscillations do not modify the giant magnetoresistance, and the magnetoresistance oscillatory extrema, i.e., maxima and minima, disappear rather asymmetrically with increasing I
dc. The results suggest the interpretation that the I
dc serves to suppress scattering between states near the Fermi level in a strong magnetic field limit.
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