We report on observation of a fine structure of microwave-induced resistance oscillations in an ultraclean two-dimensional electron gas. This fine structure is manifested by multiple secondary sharp extrema, residing beside the primary ones, which emerge at high radiation power. Theoretical considerations reveal that this fine structure originates from multiphoton-assisted scattering off short-range impurities. Unique properties of the fine structure allow us to access all experimental parameters, including microwave power, and to separate different contributions to photoresistance. Furthermore, we show that the fine structure offers a convenient means to quantitatively assess the correlation properties of the disorder potential in high-quality systems, allowing separation of short- and long-range disorder contributions to the electron mobility.
Bibliographical noteFunding Information:
We thank M. Khodas for discussions. The work at the University of Minnesota was funded by the NSF Grant No. DMR-1309578. The work at the University of Regensburg was funded by the German Research Foundation (DFG). The work at Princeton University was funded by the Gordon and Betty Moore Foundation through the EPiQS initiative Grant No. GBMF4420, and by the National Science Foundation MRSEC Grant No. DMR-1420541. Preliminary measurements were performed at the National High Magnetic Field Laboratory, which is supported by NSF Cooperative Agreement No. DMR-0654118, and by the State of Florida.