Phase Separation In Cuprate Superconductors Proceedings Of The Workshop

Phase Separation In Cuprate Superconductors - Proceedings Of The Workshop

The main objective of this workshop was to review and discuss the electronic and chemical properties of layered cuprate superconductors. These are doped antiferromagnetic (AFM) insulators, and there is the possibility of a dynamic phase separation into metallic clusters and AFM areas. A clarification on the existence and the mechanism of such a phase separation is believed to be crucial for the understanding of high-Tc superconductivity in cuprates.On the one hand, theoretical and recent experimental indications in favor of this possibility were presented, on the other hand experimental papers expressing more skeptical views were also delivered. Related work on phase separations of chemical and structural origin was also included, followed by contributions on the question; “If phase separation is present, what is the pairing mechanism in the metallic clusters?”.

Phase Separation in Cuprate Superconductors

Phase Separation in Cuprate Superconductors

Phase separation has become a fascinating subject in the discussion of cuprate superconductors. All these materials have layered structures containing CU02 planes as the most important building blocks. They are coupled only weakly so that the electronic properties show a nearly two-dimensional behaviour. Due to correlations the undoped compounds are insulators of the Mott Hubbard type exhibiting long-range antiferromagnetic order. Upon doping a rich scenario of physical phenomena appears: Even at low hole concentra tions the antiferromagnetic ordering temperature is reduced drastically and spin-glass behaviour as well as a hopping type conductivity can be observed. Further doping leads to metallic-like conductivity and below Tc to super conductivity. In this doping regime antiferromagnetic fluctuations are still observed. At very high charge carrier densities superconductivity is lost and the systems show pure metallic conduction without ,magnetic correlations. One of the most interesting phenomena in high-T c research is the interplay between magnetism and conductivity or superconductivity. Especially the behaviour of charge carriers in the antiferromagnetic background raises a number of open questions. Two scenarios become possible: the carriers tend to delocalize over the whole crystal forming a homogeneous state with band-like structure or they separate into hole-rich (conducting, superconducting) and hole-poor (insulating, antiferromagnetic) phases leading to an inhomogeneous structure.