The current-voltage characteristic and voltage spectrum of a Josephson junction under the action of current pulses are studied within the framework of a resistive shunt model. The possibility of using Josephson junctions made of high-temperature superconductors to create a quantum synthesizer of alternating voltage has been studied.

The influence of the contact resistance of the interface of the YBCO/Au structure on the transport and microwave properties of arrays of high-temperature bicrystal Josephson junctions embedded in a coplanar transmission line has been studied. The current-voltage characteristics of Josephson structures fabricated using various technologies are studied: in situ and ex situ with annealing in an oxygen atmosphere. The results obtained can be used to create a quantum ac voltage generator based on high-temperature Josephson junctions. Keywords: high-temperature superconductors, Josephson junctions, microwave, contact resistance.

The influence of the contact resistance of the interface of the YBCO/Au structure on the transport and microwave properties of arrays of high-temperature bicrystal Josephson junctions embedded in a coplanar transmission line has been studied. The current-voltage characteristics of Josephson structures fabricated using various technologies are studied: in-situ and ex-situ with annealing in an oxygen atmosphere. The results obtained can be used to create a quantum ac voltage generator based on high-temperature Josephson junctions.

Using the near-field microwave microscopy method, the temperature dependence of third harmonics power P3ω(T) of the MoN/Al superconductor–normal metal structures with the proximity effect is studied. The presence of a secondary (low-temperature) maximum and zeroings is detected in the P3ω(T) dependence of the MoN/Al structure, which disappear upon applying a weak magnetic field perpendicular to the plane of the structure.

Using the method of near-field microwave microscopy, we investigated the temperature dependence of the third harmonic power P3ω (T) of superconductor – normal metal MoN / Al structures with proximity effect. The presence of an additional (low-temperature) maximum and vanishing in the dependence P3ω (T) for the MoN / Al structure, which disappear when a weak perpendicular magnetic field is applied.

A commercially available compact Josephson voltage standard N4-21 based on high-temperature superconductor Josephson junctions with dry nitrogen temperature cooling is presented. The cryocooler unit of the voltage standard including the cryogenic system and the high-temperature superconductivity Josephson array chip is described. The measured relative standard uncertainties between output voltages of N4-21 and the primary state voltage standard of Russia are only a few parts in 10 8 . Such low uncertainties are sufficient for the application of voltage standard N4-21 in the highest-level metrology. The implementation of the link between Josephson junctions and Zener diodes largely eliminates the uncertainty contributions associated with Zeners nonlinear drift, environmental effects, and the impact due to shipping.

AbstractAn experiment on the observation of the effect of transmitting the transverse spin magnetization in spin-exchange collisions of cesium atoms with optically aligned rubidium atoms is described.

The principles for building the multivalued N4-21 voltage standard based on the precision properties of Zener diodes and the quantum mechanical properties of high-temperature superconductor Josephson junctions operating at 77 K are discussed. The metrological characteristics of the new voltage standard are presented. The relative uncertainty in the output voltages of the standard at 1 and 10 V is found to be less than 5·10–8.

A commercially available Josephson voltage standard based on high temperature superconductor Josephson junctions with a liquid nitrogen free cooling is presented. The results of the calibrations of an electronic DC reference Fluke 732B and a Keithley nanovoltmeter 2182 with uncertainties equal to a few parts in 108 demonstrate the suitability of the application of a N4-21 in the highest-level metrology. The implementation of a link between Josephson junctions and Zener diodes largely eliminates the uncertainty contributions associated with Zeners non-linear drift, environmental effects and the impact due to shipping.

Abstract—Temperature dependences of the third-harmonic power for the (Na0.3K0.7)xFe2 – ySe2 sodium–potassium ferroselenide single crystals have been investigated by nonlinear near-field microwave microscopy. The temperature dependence of magnetic susceptibility at a frequency of 100 kHz for this compound has been measured. The experimental results suggest a double-gap structure of the (Na0.3K0.7)xFe2 – ySe2 superconductor.

Developing the earlier results of Aslamazov et al (1986 Soy. Phys. JETP 64 1051) we perform a detailed study of the superconducting properties of a bilayer consisting of highly disordered superconducting (S) and low-resistive normal metal (N) films We demonstrate theoretically and experimentally that the screening and transport properties of such a SN bilayer can be considerably enhanced compared with the single S film. Such modification originates from the proximity-induced superconductivity in the N film and it is not related to enhanced vortex pinning in the SN hybrid. In particular, the coverage of superconducting NbN and MoN films by a thin Ag or Al layer is responsible for enhancing the diamagnetic response and the critical current I-c of the SN microbridge by several times and the appearance of the diode effect in a parallel magnetic field. Due to peculiar temperature dependence of I-c and the magnetic field penetration depth, such SN bilayers can be of potential interest for designing different types of superconducting bolometers and detectors.

An experiment on the observation of the effect of transmitting the transverse spin magnetization in spin-exchange collisions of cesium atoms with optically aligned rubidium atoms is described.

We demonstrate, both theoretically and experimentally, that thin dirty superconductor-normal metal bilayer with resistivity of normal metal $ρ_N$ much smaller than normal-state resistivity of superconductor $ρ_S$ has unique superconducting properties. First of all the normal layer provides the dominant contribution to the diamagnetic response of whole bilayer structure in wide temperature interval below the critical temperature due to proximity induced superconductivity. Secondly, the presence of the normal layer may increase the critical current $I_c$ in several times (the effect is not connected with enhanced vortex pinning), provides strong temperature dependence of both $I_c$ and effective magnetic field penetration depth even at temperatures much below the critical one and leads to the diode effect in parallel magnetic field. Besides of general interest we believe that the found results may be useful in construction of different kinds of superconducting detectors.

Abstract —Temperature dependences of the third-harmonic power for the (Na_0.3K_0.7)_ x Fe_2 – _ y Se_2 sodium–potassium ferroselenide single crystals have been investigated by nonlinear near-field microwave microscopy. The temperature dependence of magnetic susceptibility at a frequency of 100 kHz for this compound has been measured. The experimental results suggest a double-gap structure of the (Na_0.3K_0.7)_ x Fe_2 – _ y Se_2 superconductor.

Исследованы ВТСП бикристаллические переходы шириной до 50 mum на сапфировых подложках. Измерены зависимости величины критического тока от температуры и внешнего магнитного поля для таких контактов. При температуре 77 K получены ступени Шапиро на ВАХ с напряжением порядка 150 muV при облучении на частоте 73 GHz джозефсоновского перехода на сапфировой подложке. Проанализирована возможность использования таких контактов в эталонах напряжения при температуре 77 K в области СВЧ и терагерцовых частот. Авторы благодарят за частичную поддержку гранты РФФИ N 15-02-05793, N 15-42-02469 (р-поволжье), N 16-02-00727, а также грант РНФ N 15-12-10020. В работе использовано оборудование ЦКП "Физика и технология микро- и наноструктур". DOI: 10.21883/FTT.2017.11.45047.06k

HTS bicrystal junctions up to 50 μm wide on sapphire substrates have been studied. The dependences of the critical current on the temperature and external magnetic field of these contacts have been measured. The irradiation of the Josephson junction on a sapphire substrate at the frequency of 73 GHz at the temperature of 77 K resulted in the appearance of Shapiro steps in the current–voltage characteristic (IVC) at the voltage of 150 μV. The possibility of using such contacts in voltage standards at the temperature of 77 K in the ranges of microwave and terahertz frequencies has been analyzed.

This paper presents the results of investigations of the high-frequency properties of multi-junction Josephson circuits based on high-temperature superconductors and the specific features of their use in voltage standards.

A practical dc voltage standard with output voltages Ł/hts from 0.1 V to 10 V using high temperature superconductor (HTS) arrays of Josephson junctions cooled to 77 K was characterized. HTS arrays with increased current margins and the voltage divider with a high stability of the divider's coefficients enable stable and reproducible automated calibration of the new HTS standard. The direct comparison of U HTS against the voltage generated on an array of niobium Josephson junctions cooled to 4.2 K reveals the agreement of voltages at 1 V level with a Type A uncertainty equal to a few parts in 10 8 .