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

Abstract

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 x Ga 1−x As/InP and GaAs/Al x Ga 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.

Phase diagram of quantum Hall breakdown and nonlinear phenomena for InGaAs/InP quantum wells

“…7. The values of the exchange-enhanced g-factor determined by thermal activation measurements here are consistent with those extracted by the same technique and reported in earlier work for similar materials [21,63]. Notable, however, the estimated values for |g * o | from the rescaled method B approach are a factor of ∼2-3 times higher than those from the thermal activation measurements.…”

“…This dip is a signature of the zero current anomaly (ZCA) described in Ref. 21. In fact, the ZCA can be observed over a wide range of B-field provided that r xx is not zero in the vicinity of zero current over a current range exceeding ∼0.4 µA (see also Fig.…”

“…The distinctive dark blue diamond-shaped regions in the map of r xx identify where r xx ∼0. These regions are the so-called transport diamonds [21]. In the map of r xy too, diamonds are visible within which the r xy is quantized.…”

“…Studenikin et al [21] described basic properties of the ZCA for InGaAs/InP Hall bars, but only for B-fields up to ∼5 T and for an electron density ∼5.3×10 11 cm −2 , so filling factors no lower than ν=5 were investigated. The ZCA FWHM was found to be ∼2.1 µA (∼0.25 µA) for a 100 µm (10 µm) wide Hall bar, so this indicates, consistent with the FWHM 0.4 µA for the 15 µm wide Hall bar measured here, that the FWHM is proportional to the Hall bar width [77].…”

Zero-differential conductance of two-dimensional electrons in crossed electric and magnetic fields

“…Recently a strong nonlinear response of two dimensional electrons was observed in a geometry in which a nonlocal electron transport, associated with the propagation of the edge states or/and skipping orbits [16][17][18][19][20][21][22][23] , plays the dominant role 15 . The observation of the nonlocal nonlinear response has raised a question regarding a possibility of the significant contribution of the edge states and/or skipping orbits to the nonlinear transport of 2D electrons observed in the Hall bar geometry [24][25][26][27][28][29][30][31][32][33][34][35] and, thus, the applicability of the currently accepted theoretical approach 7 to the observed nonlinearity. We should note that in the Hall bar geometry a separation between the local and the nonlocal contributions to the electron conductance is a challenging problem.…”