Selected results of department 23

Sorting of very small particles dispersed in a fluid is a crucial problem of microfluidics and nanofluidics. A small pump pushing the fluid back and forth keeps the system very far from equilibrium. We show that combined action of inertial hydrodynamic effects plus Brownian motion leads to rectification of particle flow. We computed the average particle velocity analytically. This velocity is strongly sensitive to particle size, which promises high eficiency of sorting. The whole text »

Iron atoms adsorbed on a platinum surface were probed by the scanning tunneling microscope under changing conditions (changes of temperature, presence or absence of hydrogen). Theoretical analysis of the observed magnetic behavior indicates that these atoms behave as the so-called Hund's impurities. These impurities can be identified as building blocks of one class of high-temperature superconductors. The whole text »

The archetypal molecular bridge – a single level molecular island connected by tunneling junctions to two massive leads – acquires new properties, if the leads are ferromagnetic metals. We have studied transient effects induced by suddenly connecting the leads in the parallel geometry. The tunneling is spin dependent and a local magnetization is formed on the level originally empty. The process depends on the strength U of the local electron-electron interaction and on the structure of the tunneling functions. A model prediction of the time evolution of the transient local magnetization is shown in the figure for reasonable values of U. The incipient coherent oscillations, almost independent on U, are damped. The saturation magnetization is first zero, for U increasing from zero, then negative, i.e. opposite with respect to the magnetization of the leads. At a critical value of U, the saturation magnetization reverts and further depends but weakly on increasing U. The whole text »