****NON-TECHNICAL ABSTRACT**** This award supports experimental investigation of electronic behavior in a far-from-equilibrium system in a semiconductor quantum device, where surprising new effects have been recently discovered. For example, as discovered under prior NSF support, electrical transport in a semiconductor device can exhibit vanishing resistance when it is exposed to microwaves. This research project will investigate the effects of microwaves combined with small magnetic fields on the electronic transport in these devices. Additional experiments will image the electron flow pattern in the microwave-induced zero-resistance states using a unique microscope sensitive to magnetic fields. Understanding of fundamental properties of a semiconductor device driven by microwaves is directly relevant to emerging issues in future technologies such as "spintronics" (using the magnetic as well as electrical properties of electrons in devices) and "quantum information processing" (using quantum mechanical behavior to store and process information). The research will be carried out by graduate students and will also include the participation of undergraduate students. The graduate students will learn semiconductor physics, microwave technology, and imaging techniques, which will serve them well for employment in the national research infrastructure and high-technology industry.
The high-mobility two-dimensional electron system (2DES) provided by the state-of-the-art GaAs/AlGaAs technology is a clean laboratory for many-electron physics. This individual investigator award supports experimental investigations of a new regime of 2D physics; the quantum transport in 2DES that is subjected to far-from-equilibrium conditions. The subject matter includes the newly discovered phenomenon of radiation-induced resistance oscillations and the zero-resistance/zero-conductance states in a 2DES exposed to millimeter wavelength electromagnetic waves, dc current-induced magnetoresistance oscillations and nonlinear transport, and nonlinear optical effects in the millimeter wave regime and their influence to dc electronic transport. The project will expand beyond the standard dc transport, to include imaging experiments on the current flow pattern in microwave-induced zero-resistance states using a low temperature scanning Hall probe microscope. It will explore the electron flow pattern formation in the semi-classical and quantum regimes in a microwave-driven electronic system. The studies will be carried out by graduate students and will also include the participation of undergraduate students. The graduate students will learn semiconductor physics, microwave technology, and imaging techniques, which will serve them well for employment in the national research infrastructure and high-technology industry.
