Two Reviews On Unconventional Superconductivity

In recent weeks, there were two very good review articles on the physics of superconductivity, focusing especially on the so-called unconventional superconductivity. This includes the ruthenates, the cuprates, and the iron-based superconductors.

The first review was by Mike Norman, which appeared in a recent issue of Science (Science 332, 196 (2011)).

Abstract: During the past few decades, several new classes of superconductors have been discovered. Most of these do not appear to be related to traditional superconductors. As a consequence, it is felt by many that for these materials, superconductivity arises from a different source than the electron-ion interactions that are at the heart of conventional superconductivity. Developing a rigorous theory for any of these classes of materials has proven to be a difficult challenge, and will continue to be one of the major problems in physics in the decades to come.

The second review article was by G. R. Stewart on the iron-based superconductors. It is to appear in an upcoming issue of Rev. Mod. Phys.

Abstract: Kamihara and coworkers' report of superconductivity at Tc = 26 K in fluorine-doped LaFeAsO inspired a worldwide effort to understand the nature of the superconductivity in this new class of compounds. These iron pnictide and chalcogenide (FePn/Ch) superconductors have Fe electrons at the Fermi surface, plus an unusual Fermiology that can change rapidly with doping, which lead to normal and superconducting state properties very different from those in standard electron-phonon coupled 'conventional' superconductors. Clearly superconductivity and magnetism/magnetic fluctuations are intimately related in the FePn/Ch - and even coexist in some. Open questions, including the superconducting nodal structure in a number of compounds, abound and are often dependent on improved sample quality for their solution. With Tc values up to 56 K, the six distinct Fe-containing superconducting structures exhibit complex but often comparable behaviors. The search for correlations and explanations in this fascinating field of research would benefit from an organization of the large, seemingly disparate data set. This review attempts to provide an overview, using numerous references, with a focus on the materials and their superconductivity.

Lots of things to read. The article by Norman, especially, has a very compact summary of the development of superconductivity in general, and what is meant by "unconventional" superconductivity.

Zz.