Superconductivity without phonons

• Published in: Nature 2007-12, Vol.450 (7173), p.1177-1183
• Main Authors: Monthoux, P., Pines, D., Lonzarich, G. G.
• Format: Article
• Language: English
• Subjects: Attraction; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystal lattices; Crystal structure; Degrees of freedom; Electronics; Electrons; Exact sciences and technology; Humanities and Social Sciences; Magnetic properties; Mathematical analysis; multidisciplinary; Particle physics; Phonons; Physics; review-article; Science; Science (multidisciplinary); Superconductivity; Theory and models of superconducting state
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature06480

Who needs phonons? The 'classic' form of superconductivity was finally explained by the Nobel-winning BCS (Bardeen-Cooper-Schrieffer) theory in the 1950s, as a superfluid of electron pairs interacting via the exchange of phonons. That done, theorists asked if the deformable lattice provided by phonons was essential for superconductivity. It wasn't, as shown by the subsequent discovery of a series of 'unconventional' superconductors. In a Review Article, Phillipe Monthoux, David Pines and Gilbert Lonzarich present a restatement of the magnetic interaction model that is emerging as a powerful framework for interpreting superconductivity without phonons. The idea of superconductivity without the mediating role of lattice vibrations (phonons) has a long history. It was realized soon after the publication of the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity 50 years ago that a full treatment of both the charge and spin degrees of freedom of the electron predicts the existence of attractive components of the effective interaction between electrons even in the absence of lattice vibrations—a particular example is the effective interaction that depends on the relative spins of the electrons. Such attraction without phonons can lead to electronic pairing and to unconventional forms of superconductivity that can be much more sensitive than traditional (BCS) superconductivity to the precise details of the crystal structure and to the electronic and magnetic properties of a material.