Nanoscale real-time detection of quantum vortices at millikelvin temperatures.

Since we still lack a theory of classical turbulence, attention has focused on the conceptually simpler turbulence in quantum fluids. Reaching a better understanding of the quantum case may provide additional insight into the classical counterpart. That said, we have hitherto lacked detectors capable of the real-time, non-invasive probing of the wide range of length scales involved in quantum turbulence. Here we demonstrate the real-time detection of quantum vortices by a nanoscale resonant beam in superfluid 4He at 10 mK. Essentially, we trap a single vortex along the length of a nanobeam and observe the transitions as a vortex is either trapped or released, detected through the shift in the beam resonant frequency. By exciting a tuning fork, we control the ambient vortex density and follow its influence on the vortex capture and release rates demonstrating that these devices are capable of probing turbulence on the micron scale.

Non-contact scanning probe technique for electric field measurements based on nanowire field-effect transistor.

We report on the new active tip for scanning probe microscopy allowing the simultaneous measurements of surface topography and its potential profile. We designed and fabricated a field-effect transistor with nanowire channel located on the apex of silicon-on-insulator small chip. The field-effect transistor with nanowire channel was selected due to its extremely high electric field sensitivity even at room temperature. We developed the scanning probe operated in the tuning fork regime and demonstrated its reasonable spatial and field resolution. The proposed device can be a unique tool for high-sensitive, high-resolution, non-destructive potential profile mapping of nanoscale objects in physics, biology and material science. We discuss the ways to optimize the sensor charge sensitivity to the theoretical limit which is 10-3e/Hz-1/2 at room temperature.

Sequential reduction of the silicon single-electron transistor structure to atomic scale.

Here we present an original CMOS compatible fabrication method of a single-electron transistor structure with extremely small islands, formed by solitary phosphorus dopants in the silicon nanobridge. Its key feature is the controllable size reduction of the nanobridge in sequential cycles of low energy isotropic reactive ion etching that results in a decreased number of active charge centers (dopants) in the nanobridge from hundreds to a single one. Electron transport through the individual phosphorous dopants in the silicon lattice was studied. The final transistor structure demonstrates a Coulomb blockade voltage of ∼30 mV and nanobridge size estimated as [Formula: see text]. Analysis of current stability diagrams shows that electron transport in samples after the final etching stage had a single-electron nature and was carried through three phosphorus atoms. The fabrication method of the demonstrated structure allows it to be modified further by various impurities in additional etching and implantation cycles.

Single-electron tunneling through an individual arsenic dopant in silicon.

We report the single-electron tunneling behaviour of a silicon nanobridge where the effective island is a single As dopant atom. The device is a gated silicon nanobridge with a thickness and width of ∼20 nm, fabricated from a commercially available silicon-on-insulator wafer, which was first doped with As atoms and then patterned using a unique CMOS-compatible technique. Transport measurements reveal characteristic Coulomb diamonds whose size decreases with gate voltage. Such a dependence indicates that the island of the single-electron transistor created is an individual arsenic dopant atom embedded in the silicon lattice between the source and drain electrodes, and furthermore, can be explained by the increase of the localisation region of the electron wavefunction when the higher energy levels of the dopant As atom become occupied. The charge stability diagram of the device shows features which can be attributed to adjacent dopants, localised in the nanobridge, acting as charge traps. From the measured device transport, we have evaluated the tunnel barrier properties and obtained characteristic device capacitances. The fabrication, control and understanding of such "single-atom" devices marks a further step towards the implementation of single-atom electronics.

[Insulin regulation of 2 kinetically different types of calcium current]. / Reguliatsiia insulinom dvukh kineticheski razlichnykh tipov kal'tsievogo toka.

At least two kinetically different kinds of calcium current are shown to exist in the frog atrial cells. The current with faster activation kinetics is usually depressed by insulin. Insulin also increases the amplitude of the slower calcium current. Pretreatment of atrial cells with cycloheximide does not change the effect of insulin on the fast calcium current but dramatically facilitates the insulin-induced activation of the slower calcium current.

[Modification by cycloheximide of the effects of insulin on the transport of calcium by sarcolemma of the myocardium]. / Modifikatsiia tsiklogeksimidov éffektov insulina na transport kal'tsiia sarkolemmoi miokarda.

The inhibitory effect of insulin on Ca2+-current was supposed to be due to activation of phosphoproteinphosphotases stimulated by a specific intracellular insulin messenger. The results obtained support the above suggestion. Pretreatment of myocardial preparation with cycloheximide in low concentrations completely blocks the inhibitory insulin effect on Ca2+-current due, probably, to a decrease in peptide formation. Moreover, prolonged effect of the hormone involves a considerable increase of the current as compared to its initial value. Possible mechanisms of modifying effect of cycloheximide on the function of insulin-dependent regulatory system in the myocardium, are discussed.