Synchronization of high-frequency oscillations of phase-slip centers in a tin whisker under microwave radiation

Current-voltage characteristics of a system with a variable number of phase-slip centers resulting from phase separation in a tin whisker under external microwave field with a frequency \Omega/2\pi\=35-45 GHz have been studied experimentally. Emergence and disappearance of steps with zero slope in a whisker's current-voltage characteristic at U_{m/n}=(m/n)U_{\Omega}, where m and n are integers and U_{\Omega} is determined by Josephson's formula \hbar\Omega=2eU_{\Omega}, have been investigated. Microwave field generated by phase-slip centers is nonharmonic, and the system of phase-slip centers permits synchronization of internal oscillations at a microwave frequency by an external field with a frequency which is the n-th harmonic of internal oscillations. The estimated microwave power generated by a whisker is 10^{-8} W. Stimulation of superconductivity in a current-carrying whisker has been detected.Comment: 7 pages, 6 figures, RevTex4. Several of the translated words defined more exactl

Aharonov-Bohm effects in nanostructures

Measurements of the Little-Parks oscillations at measuring current much lower than the persistent current give unambiguous evidence of the dc current flowing against the force of the dc electric field because of the Aharonov-Bohm effect. This result can assume that an additional force is needed for description of the Aharonov-Bohm effect observed in semiconductor, normal metal and superconductor nanostructures in contrast to the experimental result obtained recently for the case of the two-slit interference experiment.Comment: 3 pages, 2 figure

Temperature dependence of the resistance of a phase-slip line in a thin superconducting film

An experimental investigation was made of the temperature dependence of the first step of a phase-slip line in a thin superconducting tin film. The depth of penetration of a nonequilibrium longitudinal electric field into the superconductor was determined near the critical temperature. A comparison was made with theoretical investigations of one-dimensional structures containing phase-slip centers. The experimental results were found to be in good agreement with the theory when the mechanism of mixing of electron-like and hole-like branches of the quasiparticle spectrum was governed by the elastic scattering of the excitations. This was one more experimental confirmation that a phase-slip line is a two-dimensional analog of a phase-slip center.Comment: 3 pages, 2 figures, Revtex4. Numeric format(separators)in Figures change

Two permitted states of superconducting ring observed at measurements of its critical current

Magnetic dependencies of the critical current of superconducting, aluminium rings, with homogeneous section and with small narrow spot, are measured. Only permitted state at each magnetic flux value is observed in the conventional ring because of strong discreteness of its spectrum. But two states are observed because of the small narrow spot.Comment: 3 pages, 2 figure, Presented at the 34 Meeting on the Low Temperature Physics, 26-30 September 2006, Loo, Russi

The dc voltage proportional to the persistent current observed on system of asymmetric mesoscopic loops

The observations of the dc voltage proportional to the persistent current on system of asymmetric superconductor loops at a non-zero resistance raise a question on a nature of this quantum phenomenon and its possibility in semiconductor and normal metal mesoscopic loops.Comment: 3 pages, 3 figure

Observation of the Little-Parks Oscillations in a System of Asymmetric Superconducting Rings

Little-Parks oscillations are observed in a system of 110 series-connected aluminum rings 2000 nm in diameter with the use of measuring currents from 10 nA to 1000 nA. The measurements show that the amplitude and character of the oscillations are independent of the relation between the measuring current and the amplitude of the persistent current. By using asymmetric rings, it is demonstrated that the persistent current has clockwise or contra-clockwise direction. This means that the total current in one of the semi-rings may be directed against the electric field at measurement of the Little-Parks oscillations. The measurements at zero and low measuring current have revealed that the persistent current, like the conventional circulating current, causes a potential difference on the semi-rings with different cross sections in spite of the absence of the Faraday's voltage.Comment: 5 pages, 6 figure

Experimental investigations of the change with magnetic flux of quantum number in superconducting ring

The magnetic dependencies of the critical current of aluminum ring with asymmetric link-up of current leads have been measured in order to clear up the essence of the paradoxical absence of the jump of the critical current at the quantum number change revealed before at the measurements of asymmetric superconducting ring. The measurements have shown that the experimental and theoretical dependencies agree in the region of magnetic field corresponding to integer numbers of the flux quantum and disagree at the half of the flux quantum. The jump is not observed as well as in the asymmetric rings.Comment: 3 pages, 2 figures, for the Proceedings of 19th International Symposium "NANOSTRUCTURES: Physics and Technology", 20 - 25 June 2011, Ekaterinburg, Russi

Multiple and single measurements of a mesoscopic quantum system with two permitted states

Mesoscopic loop is proposed in many works as possible solid-state quantum bit, i.e. two-state quantum system. The quantum oscillations of resistance and of rectified voltage observed on asymmetric superconducting loops give evidence of the two states at magnetic flux divisible by half of the flux quantum. But our measurements of quantum oscillations of the critical current of these loops have given results coming into irreconcilable contradictions with result of the observations of the quantum oscillations of resistance.Comment: 3 pages, 3 figure

Could two degenerate energy states be observed for a superconducting ring at Φ0\Phi_{0}/2?

The Little-Parks oscillations of the resistance and the quantum oscillations of the rectified voltage observed for asymmetric superconducting Al rings give experimental evidence of two degenerate energy states at the magnetic flux $\Phi_{0}$/2. The quantum oscillations of the critical current as a function of magnetic field have also been measured. On the one hand, these oscillations confirm that the quantum oscillations of the rectified voltage are a consequence of periodical dependence of the asymmetry of the current-voltage curves and, on the other hand, comparison of the oscillations with Little-Parks measurements results in contradiction.Comment: 4 pages, 6 fige

Thin-Film Aluminum Microstructure as a Hot-Electron Microwave Radiation Detector

We have found that the thin film aluminum structures shaped into a chain of micron sized islands connected by narrow isthmuses, can modify their electrical and structural properties under microwave radiation. As a result, at the temperature of 4.2 K the film structures turn into a kind of lateral periodic structure N-S-N, where N is for normal islands, S is for superconducting isthmuses. Current-voltage characteristics of the samples, as well as changes of these characteristics under low power radiation, have been studied over the temperature range from 1.3 to 10 K. The sensitivity of a structure as a microwave detector runs 10^{5} V/W.Comment: 4 pages, 4 figures, RevTex