MAGNETIC AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc SUPERCONDUCTORS

Abstract

High-Tc superconductors, distorted-perovskite cuprates, are derived, by means of suitable doping, from a Mott-insulating and antiferromagnetic parent material. The most important ingredient of their structure is the stacks of Cu-O planes which carry superconductivity. Magnetic, transport and other properties that characterize the supercon-ducting state are very unusual and highly anisotropic. Density of states at the Fermi level in these materials is rather small but Tc is very high (highest reported Tc~125 K). In the high-Tc systems that contain magnetic moment bearing rate earth (RE)-atoms, antiferromagnetic ordering (TN<2 K) of RE-moments coexists with superconductivity. Some of them are ideal two-dimensional magnetic systems. Flux line lattices in these materials have rather unusual structural properties. There are both hole-type as well as electron-type superconductors. The available experimental evidence does not favour odd-parity pairing. It is not yet clear, however, whether even-parity pairing is d-wave or s-wave type. Antiferromagnetic fluctuations may be possible mechanism of Cooper pairing. Anyonic superconductivity is ruled out.