Large upper critical field and irreversibility field in MgB2 wires with SiC additions

Anisotropy of the upper critical field and critical current in single crystal MgB2

Geometrical barriers and lower critical field in MgB2 single crystals

Transport and magnetic critical current in superconducting MgB2 wires

Direct comparison of the magnetic and transport critical current density (Jc) for the same pieces of copper-sheathed MgB2 wires shows a large discrepancy in magnitude and field dependence of the two. The value of magnetic Jc can differ from the value of transport Jc by a factor of 10 or more. This discrepancy does not occur merely because of the difference in the voltage at which the magnetic a...

Upper critical field in anisotropic superconductors.

Anisotropic superconductivity has been studied in a variety of one-dimensional, ' intercalated, s and artificially prepared" " systems. Much of the experimental work in these systems is related to measurements of the temperature and angular dependence of the upper critical fields H, 2. In many cases, the experiments determine the critical field at which surface superconductivity nucleates, i.e....

Irreversibility in Quantum Field Theory

It is shown how the programme of decoherence can be applied in the context of quantum field theory. To illustrate the role of gauge invariance, we first discuss the charge superselection rule in quantum electrodynamics in some detail. We then present an example where macroscopic electromagnetic fields are “measured” through interaction with charges and thereby rendered classical. A central role...