Fermi surface of a parent  ferropnictide (LaFeAsO),  colored according to the Fermi velocity
Fermi surface of a parent ferropnictide (LaFeAsO), colored according to the Fermi velocity

Superconducting materials are used in a wide variety of defense and civilian technologies. Navy applications include superconducting motors for electric drives, microwave devices, superconducting magnets, and mine sweeping.

The Center for Computational Materials Science has a long history of supporting the Navy's interest in superconducting materials. First principles calculations were used, starting in the mid-1970's, to calculate the electron-phonon interactions in elemental metals, carbides, nitrides, hydrides and the A15 compounds. The goals of the work were to advance understanding of the microscopic basis of superconductivity, to establish a predictive first principles framework for the investigation of superconducting materials, and to identify new phases with potentially high critical temperatures for experimental investigation.

Recent work in the Center is continuing this line of research by applying modern linear-response methods combined with numerical solvers for the Eliashberg equations to address electron-phonon mediated superconductivity, especially in novel materials such as MgB2 or CaC6. This has resulted in a new understanding of the materials -- for example, the prediction of two-gap superconductivity in MgB2 -- as well as suggestions for improved materials -- for example, the prediction of still higher critical temperatures in the as yet unsynthesized compound, Li2B2-xCx. The Center also has a significant effort investigating materials with both magnetism and superconductivity, particularly unconventional superconductivity mediated by spin fluctuations, as in Sr2RuO4, NaxCoO2.yH2O, and the newly discovered ferropnictides.
Principal Investigator: Igor Mazin