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Microwave photo-response of two-dimensional electron systems: Interplay of collective and single-particle excitations

Ziel

The project objectives consist of (i) creation of a detailed picture of the microwave photoresponse of two-dimensional electron systems (2DES) based on intensive experimental investigations and development of a photoresponse theory and (ii)clarifying mechanisms of operation of microwave detectors and spectrometers recently proposed by authors of the proposal. In the experimental part of the project, electrical detection of the microwave radiation, which includes the giant magnetoresistance oscillations (GMO), the zero resistance states (ZRS), and the magnetic-field-periodic oscillations will be studied simultaneously with spectra of the resonant microwave absorption. One of the key ideas of the GMO theory, non-equilibrium occupation of the disorder-broadened Landau levels, will be verified experimentally by the method of optical luminescence and in experiments with two-color irradiation. The domain structure, proposed to explain ZRS, will be checked with the use of an appropriately arranged set of potential probes. Interference of the edge magnetoplasmons as the origin of the B-periodic oscillations will be examined. Spectra and dispersion of collective excitations in finite-size samples will be studied by optical detection of the microwave resonant absorption. The retardation and polariton effects in the spectra will be investigated. In the theoretical part of the project, the theory of the microwave photoresponse will be further developed. The GMO theory will incorporate the multiphoton processes, the spin degree of freedom, and the effect of the collective excitations. It will be generalized (i) to describe the full range of magnetic fields, from strongly overlapping to separated Landau levels, (ii) to include the case of multicolor radiation, and (iii) to consider the effects of resonant reflection and heating. In the regime of ZRS, the spatial structure of spontaneously formed domains and contribution of the thermal noise and domain wells to the sample resistance will be studied. Detailed theoretical investigation of the microwave response and plasma excitations in a 2DES for particular sample geometries will be performed. Unknown low-lying excitation modes, 1D plasmons and evolution from the 1D to the 2D mode will be studied. Influence of the finite-size effects, the presence of screening metallic electrodes in the vicinity of the 2DES (metallic gates), nonlocal and quantum-mechanical effects, electrodynamic (radiative and retardation) effects on the frequency and the damping of plasma waves will be investigated. The experimentally observed effects in the microwave photoresponse of 2DES will be explained within a unified approach including single-particle and collective excitations produced by the radiation. The basic theoretical ideas will be experimentally verified. Operation of a new type of the microwave detectors will be optimised and a prototype of CCD-camera working in the 0.1-1 THz frequency range will be fabricated.

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FORSCHUNGSZENTRUM KARLSRUHE (FZK)
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KARLSRUHE
Deutschland

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Letzte Aktualisierung: 16 März 2017

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Permalink: https://cordis.europa.eu/project/id/INTAS2005-1000008-8044/de

European Union, 2024