9 research outputs found

    Chaotic Electron Motion in Macroscopic and Mesoscopic Antidot Lattices

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    Antidot arrays consisting of a lattice of nanometer scale holes etched through a two- dimensional electron gas display distinct resistance anomalies if the period of the array is much smaller than the electron mean free path. While in conventional conductors the electrons are deflected by randomly distributed scatterers, the situation is different in antidot arrays: here, the electrons predominantly collide with the periodically arranged antidots. Due to their geometry, antidot lattices can be considered as periodically repeated Sinai billiards, known for their classically chaotic electron dynamics. Here, electron transport through two different types of antidot lattices will be discussed: in macroscopic antidot lattices the extent of the array is much larger than the phase coherence length or the elastic mean free path of the electrons while in mesoscopic ones the electrons can travel ballistically from the ‘entrance’ to the ‘exit’ of the array

    Weak Localization in Antidot Arrays: Signature of Classical Chaos

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    We study, experimentally and theoretically, quantum weak localization (WL) corrections to the classical magnetoconductivity of two-dimensional ballistic systems with regular and disordered patterns of dense antidots. We analyze the observed temperature and flux dependences of the WL using different theoretical models for the chaotic dynamics and dephasing rates. The measured resistivity curves, which deviate from those of diffusive systems, reflect chaotic motion and correlations in the classical dynamics of electrons in the antidot landscape. The results support the significance of the Ehrenfest time as a relevant time scale for ballistic WL

    Weak localization in an ensemble of ballistic cavities filled with antidots arrays

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    We present experimental data on the ballistic weak localisation in square cavities filled with antidot arrays. The weak localisation peak is cusp-like at mK temperatures and clearly deviates from a Lorentzian line shape, which is the theoretical prediction for a classical chaotic system. Although the ideal system, a Sinai billiard, is in principle purely chaotic, directly reflected, non-chaotic trajectories lead to the behaviour of a mixed system in experiment. We demonstrate this by detailed semiclassical analysis. In comparison, empty cavities of equal geometry show a sharper peak in the form of a Lorentzian. Here, imperfections of the experimental structure (boundary roughness, small- angle scattering) seem to change the dynamics of the nominally regular system to chaotic, contrary to the antidot case

    Comparative Assessment and Merit Appraisal of Thermally Assisted Machining Techniques for Improving Machinability of Titanium Alloys

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    Computer vision is presently a very relevant and important tool in both industrial manufacturing and mobile robots. As human vision is the most relevant sense to feed the brain with environmental information for decision making, computer-vision is nowadays becoming the main artificial sensor in the domains of industrial quality assurance and trajectory control of mobile robots

    Metallic implant biomaterials

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