7.6 Mechanism of High Temperature Superconductivity

The high temperature superconducting materials are of category of Type–II superconductors and show a gradual change in transition temperature as a function of the magnetic field. There has been intensive research on developing a theory for high temperature superconductivity and consequently a few mechanisms have been proposed, out of whch following two are well accepted.

First mechanism is based on the antiferromagnetic spin fluctuations in a doped system such as cuprates. Spin fluctuation tests yield information on the symmetry of the pairing wave function which, for cuprates, should be of the type dx²-y². The second model is the interlayer coupling model which states that superconductivity in a layered structure consisting of BCS-type symmetry i.e. s-wave symmetry can be enhanced by itself.

However, both of these models do not fully explain the high temperature superconductivity and there is no clear consensus.