High-temperature Superconducting Layer Research Articles

Low energy gap-like structure in YBa/sub 2/Cu/sub 3/O/sub 7-x//metal junctions

Low-energy gap-like structures were experimentally observed in different types of tunnel junctions with base electrodes of high-temperature superconductor (HTS) and upper electrodes of low-temperature superconductor (LTS) or normal metal. The resulting structures are interpreted as arising from a sum of LTS and HTS gaps resulting from the strong depression of superconductivity in HTS near the tunneling barrier due to the outdiffusion of oxygen. This conclusion is confirmed by the temperature and magnetic field dependence of the structures. The energy gap of a degraded HTS layer was found to be about 1.6 meV, with ratio 2 Delta /sub L//k/sub B/T/sub c/=4.1 and critical temperature T/sub c/ equivalent to 9 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Screened heavy polarons and their spin relaxation in high-temperature superconductors.

Large-radius polarons in the conducting layers of high-temperature superconductors have been investigated. The characteristic parameters of these polarons as functions both of the temperature and concentration of free charge carriers in the layer are calculated. The phenomenon of a giant enhancement of the spin-relaxation rate (1/${\mathit{T}}_{1}$) is predicted.

Penetration depth and microwave loss measurements with a YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−δ trilayer transmission line

A trilayer YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−δ transmission line was fabricated to measure the penetration depth of the high-temperature superconducting layers, to determine the microwave losses, and to demonstrate the potential for practical high-temperature superconductor multilayer microwave circuits. All layers were deposited onto a (100) MgO substrate by pulsed laser deposition. The superconducting films are c-axis oriented with critical temperatures of 89 K. From the phase velocity measurements, the penetration depth was found to be consistent with weak-coupled BCS theory in the local limit with a zero-temperature value of 135 nm. A simple phenomenological temperature dependence for the penetration depth is also presented. This successful trilayer fabrication process, besides allowing the determination of the penetration depth and microwave loss, also expands the possible applications of the high-temperature superconductors.

Plane polarons in the conducting layers of high temperature superconductors

The problem of the existence of a polaron induced by a heavy hole under shielding by the free electron gas is discussed. It is shown that a critical length of shielding by the free charge carriers for polaron destruction exists. The characteristic size of the polaron in a conducting substance and the energy of the electron in the polaronic well have been calculated. Both two-dimensional and three-dimensional shielding charge carriers are considered. It is shown that two-dimensional polarons in a system with two-dimensional shielding electron gas may exist in a wide concentration region.

Magnetic Field Effect on High Tc Superconductive Films

Thin film fabrication has an important role to play as a means of clarifying the basic physical properties of high-temperature superconductors. For instance, when epitaxial film growth techniques are used, crystal axes are aligned far more easily than in the bulk state, facilitating the measurement of physical properties. It is the that superconducting materials so dense that they have a critical current as high as 107 A/cm{sup 2} can be fabricated. And, if high-temperature superconducting layers could be formed epitaxially on metals, semiconductors, insulators, and magnetic materials with a junction scale of order {lambda}GL and {xi}, the method would be open for new types of superconducting devices. In this report, the authors describe thin superconducting films formed on a metal buffer layer.