Paths to Higher Temperature Superconductors

Abstract

This article discusses a 2-day workshop which was held by researchers attempting to find new superconducting materials. Topics discussed including synthesizing compounds which have the CuO[sub 2] planes in different environments, the superconducting properties of the bismuthates, fulleride superconductors, nitride synthesis and properties, molecular beam epitaxy techniques for fabricating oxide structures, etc. General guidelines for finding new superconductors are given as follows. Materials should be multicomponent structures with more than two sites per unit cell, where one or more sites not involved in the conduction band can be used to introduce itinerant charge carriers. Compositions should be near the metal-insulator Mott transition. On the insulating side of the Mott transition, the localized states should have spin-1/2 ground states and antiferromagnetic ordering the parent compound. The conduction band should be formed from antibonding tight-binding states that have a high degree of cation-anion hybridization near the Fermi level. There should be no extended metal-metal bonds. Structural features that are desirable include two-dimensional extended sheets or clusters with controllable linkage, or both.