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

Abstract

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.

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

“…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.…”

“…A brief report on our early work appears at ref. 63 . Here, we present data as a function of several parameters, and subject the observed narrow negative magnetoresistance data to an empirical fit in order to extract the characteristic lengths.…”