80 research outputs found
Microscopic examination of hot spots giving rise to nonlinearity in superconducting resonators
We investigate the microscopic origins of nonlinear rf response in
superconducting electromagnetic resonators. Strong nonlinearity appearing in
the transmission spectra at high input powers manifests itself through the
emergence of jumplike features near the resonant frequency that evolve toward
lower quality factor with higher insertion loss as the rf input power is
increased. We directly relate these characteristics to the dynamics of
localized normal regions (hot spots) caused by microscopic features in the
superconducting material making up the resonator. A clear observation of
hot-spot formation inside a Nb thin film self-resonant structure is presented
by employing the microwave laser scanning microscope, and a direct link between
microscopic and macroscopic manifestations of nonlinearity is established.Comment: 5 pages, 4 figure
Electrical breakdown of a dielectric for the formation of a superconducting nanocontact
Electrical breakdown of the dielectric nanolayer between film electrodes of
niobium and an alloy of 50% indium and 50% tin forms a bridge of this alloy
between the electrodes. The bridge resistance depends on the breakdown current.
The length of the bridge is equal to the thickness of the dielectric (30 nm),
and its diameter is 25 nm. The calculated coherence length of the alloy at 0 K
is close to the length of the bridge. The calculated critical current of a
bridge with a resistance of 1 {\Omega} at a temperature of 0 K is 2 mA. It is
concluded that such a bridge should have the properties of a Josephson contact
at a temperature lower than the critical temperature of the alloy (6.5 K).Comment: 11 pages, 7 figure
Automation of Educational Institution Documentation
The article addresses issues related to the implementation of the competence approach in order to make the teaching process of an educational institution more efficient, analyzes the reasons for diminished efficiency of putting into practice the automated systems used for university management. The authors propose the structure of an automated system, which allows the university to create the required package of teaching documents taking into account the three-level system: administrator, supervisor of educational program, and lecturer. Designing object-oriented model in the area of a special subject requires identification of business-requirements to the system. On the basis of the model of subject area and specified business-requirements, the diagram of applying variants and the schemes of functioning is constructed. The suggested system of the automated execution of teaching documents enables to reduce error rate while carrying out and implementing it due to the integrated system of conceptions and feedback between its elements
Observation of breathers in Josephson ladders
We report on the observation of spatially-localized excitations in a ladder
of small Josephson junctions. The excitations are whirling states which persist
under a spatially-homogeneous force due to the bias current. These states of
the ladder are visualized using a low temperature scanning laser microscopy. We
also compute breather solutions with high accuracy in corresponding model
equations. The stability analysis of these solutions is used to interpret the
measured patterns in the I-V characteristics
Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect
Laser Scanning Microscopy of HTS Films and Devices
The work describes the capabilities of Laser Scanning Microscopy (LSM) as a
spatially resolved method of testing high_Tc materials and devices. The earlier
results obtained by the authors are briefly reviewed. Some novel applications
of the LSM are illustrated, including imaging the HTS responses in rf mode,
probing the superconducting properties of HTS single crystals, development of
twobeam laser scanning microscopy. The existence of the phase slip lines
mechanism of resistivity in HTS materials is proven by LSM imaging.Comment: 17 pages, 21 figures, Submitted to Fizika Nizkikh Temperatur (Low
Temperature Physics
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