CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Exploitable results
Layered superconductors have been intensively studied since the discovery of the high-Tc cuprates. These materials contain one or more CuO2 layers per unit cell carrying the superconducting electrons which are separated by insulating or weakly conducting material constituting a Josephson coupling between the layers. In this project the highly anisotropic and non-linear electromagnetic properties produced by this coupling have been investigated.
In particular the surface critical field along the layers, the fluctuation contribution to the magnetisation, and the special form of the vortex structure produced by defects have been studied. These effects were investigated in close co-operation with experimentalists from Grenoble. A particularly exciting subject is the possible existence of a non-uniform superconducting state in the layers as proposed theoretically by Fulde, Ferrell, Larkin, Ovchinnikov a long time ago, which may be realised in these materials and hass now been studied both theoretically and experimentally in this project.
The multi-layer structure of the cuprate superconductors leads to a coupling between the superconducting order parameters in different layers which has implications for the Josephson effect: Besides charge fluctuations also spin-fluctuations between the CuO2 layers are possible, which in the case of interlayer-pairing can be regarded as spin-Josephson effect. The proximity effect between CuO2 layers and CuO chains may lead to a phase difference between Josephson currents in the direction along and perpendicular to the chains. Such a phase shift has been observed experimentally in corner SQUID experiments and so far has been explained by the asssumption of a d-wave superconducting order parameter in the layers. Recently the influence of non-magnetic and magnetic impurities in such systems has been studied.
The weak coupling in the direction perpendicular to the superconducting layers leads to an intrinsic Josephson effect in this direction. In this project the possibility to use this effect for the detection and amplification of radiation in the far-infrared regime has been investigated. Recently discovered structures in the current-voltage characteristic could be explained by us by the coupling between phonons and Josephson oscillations in the THz frequency regime. This new effect can be used to improve the performance of such materials as radiation detectors at high frequencies.
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