Hopes for a Hole-Doped Metal Superconductor

Last year a new record was set for a superconductor transition temperature, 40 K, for an all-metal compound (Update 530). Much more is known now about these MgB₂ materials. There is now hope that a related compound, LiBC, might operate at temperatures at high as 100 K, as much as twice as high as for MgB₂.

Warren Pickett of UC-Davis (530-752-0926, pickett@physics.ucdavis.edu) points out that the interactions that are the essence of superconductivity, the pairing of electrons brought about by the interactions between electrons and concerted flexings (phonons) in the material lattice, are potentially twice as strong in LiBC than in MgB₂, especially if holes (the momentary vacancies left behind by departed electrons) can be injected into the sample by a "field-effect" process.

This is a common procedure in transistors, where a gate electrode forces holes into a channel between the other two electrodes, thus enhancing the conductivity in that region, inducing a metallic state and producing superconductivity. A field-effect setup helped to boost the superconducting transition temperature in a crystal of carbon-60 molecules up to 117 K last year (Update 555).

The LiBC hypothesis was reported at the APS meeting and in Rosner et al., Physical Review Letters, 25 March 2002.)