High-temperature Josephson Junctions Research Articles

Влияние контактного сопротивления интерфейса YBCO|Au на транспортные и СВЧ-свойства массивов джозефсоновских контактов из высокотемпературных сверхпроводников

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.

Influence of the contact resistance of the YBCO/Au interface on the transport and microwave properties of arrays of high-temperature Josephson junctions

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.

Design Issues of HTS Bi-SQUID

We suggest a solution in principle for implementation of bi-superconducting quantum interference devices (bi-SQUIDs) on the basis of bicrystalline technology for high-temperature Josephson junctions. Optimization of the device design and parameters is discussed. Examples of the possible bi-SQUID layouts are considered.

Terahertz spectroscopy with a Josephson oscillator and a SINIS bolometer

The voltage response of a thin-film normal-metal hot-electron bolometer based on a SINIS (superconductor-insulator-normal metal-insulator-superconductor) structure to the radiation of a high-temperature Josephson junction in the terahertz frequency region was measured. Bolometers were integrated with planar log-periodic and double-dipole antennas, and Josephson junctions were integrated with log-periodic antennas. Measurements showed that the Josephson junction at a temperature of 260 mK was overheated by the transport current, so that its electron temperature exceeded 3 K at a bias voltage of 1 mV. The maximum response of a bolometer with a double-dipole antenna was observed at a frequency of 300 GHz, which agreed well with the calculated value. The Josephson radiation was observed at frequencies up to 1.7 THz. The voltage response of a bolometer reached 4×108 V/W, and the total noise-equivalent power reached 1.5×10−17 W/Hz1/2.

Preparation of ramp-type Josephson junctions using an Nd2CuO4 barrier

Ramp-type Josephson junctions with a Nd2CuO4 (NCO) barrier have been fabricated on (001)-SrTiO3 using RF magnetron sputtering. Such an NCO barrier has a highly stable T′-214 structure and is chemically compatible with the 123-superconductors. The lattice constant and thermal expansion coefficient of YBa2Cu3Oy and NCO being very similar ensures a high transparency at the superconductor/barrier interface, thus significantly increasing the reproducibility. Its resistivity is also remarkably higher than that of many currently used barrier materials. These junctions showed a typical resistively shunted junction-like current–voltage characterization and Shapiro steps under irradiation using a microwave field. The current uniformity of these junctions has also been enhanced significantly. The temperature dependence of the junction parameters and the scaling behaviour are discussed and compared with other high temperature Josephson junctions.

Remanent magnetization of high-temperature Josephson junction arrays

In this work we study the remanent magnetization exhibited by tridimensional disordered high-T c Josephson junction arrays excited by an AC magnetic field. The effect, as predicte by numerical simulations and previously verified for a low-T c array of Nb, occurs in a limited range of temperatures. We also show that the magnetized state can be excited and detected by two alternative experimental routines.

Stability and uniformity of planar high temperature Josephson junctions fabricated using nanolithography and ion damage

We have investigated the room temperature stability and the critical current uniformity of planar thin film YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// Josephson junctions. The junctions were fabricated using electron-beam lithography to define a stencil structure followed by ion damage from a conventional 200 keV ion implanter. Using this technique, we have fabricated junctions with weak link lengths of 20-100 nm that showed classical dc and ac Josephson effects at 77 K. By a suitable choice of damage and stencil width, these devices may be tuned to operate at any temperature between 1 K and the bulk transition temperature, and they may be placed anywhere on a wafer, providing a high degree of flexibility for circuit applications. Results obtained over several months showed a high level of room temperature stability, and the uniformity of the junctions was maintained.

Spectral aspect of the onset of subharmonic Shapiro steps in a chain of Josephson junctions connected in parallel

A chain of parallel-connected Josephson elements described by a resistive model is considered as a model for high-temperature Josephson junctions. The calculated spectra of the Josephson generation can account for the experimentally observed subharmonic Sapiro steps on the current-voltage characteristic and for their aperiodic dependence on the external magnetic field.

Comparative study of the stationary properties of high-T/sub c/ proximity-coupled Josephson junctions

Much recent research aimed at developing high temperature Josephson junctions for electronics applications is based on superconductor-normal metal-superconductor (SNS) edge junctions which, in some instances, exhibit excellent current-voltage characteristics, high critical current-resistance products, and low noise. We review the data available in the published literature and conclude that, despite the useful performance of these junctions, there is little evidence that the behavior of most reported high-T/sub c/ SNS devices can be described by conventional proximity effect theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-temperature Josephson junctions and their applications

Manufacturable Josephson junctions with grain-boundary and proximity barriers made it possible to demonstrate SQUID sensors having energy resolutions approaching those of commercial low-temperature SQUIDs. Results indicate that the field sensitivity of HTS SQUIDs is already adequate for most magnetometer applications.