Nonlinear magnetotransport phenomena in high-mobility two-dimensional electrons in InGaAs/InP and GaAs/AlGaAs

摘要

This paper reports on the observation and analysis of magnetotransport phenomena in the nonlinear differential resistance r_(xx) = dV_(xx)/dI of high-mobility In_xGa_(1-x)As/InP and GaAs/Al_xGa_(1-x)As Hall bar samples driven by direct current I_(dc). Specifically, it is observed that Shubnikov-de Haas (SdH) oscillations at large filling factors invert their phase at sufficiently large values of I_(dc). This phase inversion is explained as being due to an electron heating effect. In the quantum Hall effect regime the r_(xx) oscillations transform into diamond-shaped patterns with different slopes corresponding to odd and even filling factors. The diamond-shaped features at odd filling factors can be used as a probe to determine spin energy gaps. A zero current anomaly (ZCA) which manifests itself as a narrow dip in the r_(xx)(I_(dc)) characteristics at zero current is also observed. The ZCA effect strongly depends upon temperature, vanishing above 1 K while the transport diamonds persist to higher temperatures. The transport diamonds and ZCA are fully reproduced in a higher mobility GaAs/AlGaAs Hall bar structure confirming that these phenomena reflect intrinsic properties of two-dimensional systems.