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Author: Schmidt, O.G. × Start date: 2010 × DDC: 620 × Publisher: London : Nature Publishing Group ×

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Now showing 1 - 4 of 4
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    Spin-orbit coupling of light in asymmetric microcavities
    (London : Nature Publishing Group, 2016) Ma, L.B.; Li, S.L.; Fomin, V.M.; Hentschel, M.; Götte, J.B.; Yin, Y.; Jorgensen, M.R.; Schmidt, O.G.
    When spinning particles, such as electrons and photons, undergo spin–orbit coupling, they can acquire an extra phase in addition to the well-known dynamical phase. This extra phase is called the geometric phase (also known as the Berry phase), which plays an important role in a startling variety of physical contexts such as in photonics, condensed matter, high-energy and space physics. The geometric phase was originally discussed for a cyclically evolving physical system with an Abelian evolution, and was later generalized to non-cyclic and non-Abelian cases, which are the most interesting fundamental subjects in this area and indicate promising applications in various fields. Here, we enable optical spin–orbit coupling in asymmetric microcavities and experimentally observe a non-cyclic optical geometric phase acquired in a non-Abelian evolution. Our work is relevant to fundamental studies and implies promising applications by manipulating photons in on-chip quantum devices.
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    Key concepts behind forming-free resistive switching incorporated with rectifying transport properties
    (London : Nature Publishing Group, 2013) Shuai, Y.; Ou, X.; Luo, W.; Mücklich, A.; Bürger, D.; Zhou, S.; Wu, C.; Chen, Y.; Zhang, W.; Helm, M.; Mikolajick, T.; Schmidt, O.G.; Schmidt, H.
    This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO 3/Pt/Ti capacitor-like structures. Polycrystalline BiFeO 3 thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO 2/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600 C. The current-voltage (I-V) curves indicate that resistive switching can only be achieved in Au/BiFeO 3/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO 3 thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits.
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    Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries
    (London : Nature Publishing Group, 2014) Liu, X.; Si, W.; Zhang, J.; Sun, X.; Deng, J.; Baunack, S.; Oswald, S.; Liu, L.; Yan, C.; Schmidt, O.G.
    With Fe2O3 as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe2O3 nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g-1 after 1000 cycles at 2 C and 530 mAh g-1 after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous "mini-capacitors" to provide the pseudo-capacitance thus maintain the capacity at high rate.
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    Magnetoresistive emulsion analyzer
    (London : Nature Publishing Group, 2013) Lin, G.; Baraban, L.; Han, L.; Karnaushenko, D.; Makarov, D.; Cuniberti, G.; Schmidt, O.G.
    We realize a magnetoresistive emulsion analyzer capable of detection, multiparametric analysis and sorting of ferrofluid-containing nanoliter-droplets. The operation of the device in a cytometric mode provides high throughput and quantitative information about the dimensions and magnetic content of the emulsion. Our method offers important complementarity to conventional optical approaches involving ferrofluids, and paves the way to the development of novel compact tools for diagnostics and nanomedicine including drug design and screening.