Phase study of oscillatory resistances in microwave-irradiated- and dark- GaAs/AlGaAs devices: Indications of a new class of integral quantum Hall effect

摘要

We report the experimental results from a dark study and a photo-excitedstudy of the high mobility GaAs/AlGaAs system at large filling factors, $\nu$.At large-$\nu$, the dark study indicates several distinct phase relations("Type-1", "Type-2", and "Type-3") between the oscillatory diagonal- and Hall-resistances, as the canonical Integral Quantum Hall Effect (IQHE) is manifestedin the "Type-1" case of approximately orthogonal diagonal- and Hall resistance-oscillations. Surprisingly, the investigation indicates quantum Hall plateausalso in the "Type-3" case characterized by approximately "anti-phase" Hall- anddiagonal- resistance oscillations, suggesting a new class of IQHE. Transport studies under microwave photo-excitation exhibit radiation-inducedmagneto-resistance oscillations in both the diagonal, $R_{xx}$, andoff-diagonal, $R_{xy}$, resistances. Further, when the radiation-inducedmagneto-resistance oscillations extend into the quantum Hall regime, thereoccurs a radiation-induced non-monotonic variation in the amplitude ofShubnikov-de Haas (SdH) oscillations in $R_{xx}$ \textit{vs}. B, and anon-monotonic variation in the width of the quantum Hall plateaus in $R_{xy}$.The latter effect leads into the vanishing of IQHE at the minima of theradiation-induced $R_{xx}$ oscillations with increased photo-excitation. Wereason that the mechanism which is responsible for producing the non-monotonicvariation in the amplitude of SdH oscillations in $R_{xx}$ underphoto-excitation is also responsible for eliminating, under photo-excitation,the novel "Type-3" IQHE in the high mobility specimen.