Single Spin Superconductivity
W. E. Pickett, Phys. Rev. Lett. 77, 3185 (1996)
It was shown in this paper that a spin-compensated half-metallic antiferromagnetic allows the possibility of a new, axial type of superconductity, a state in which only one spin channel is superconducting. This spin S=1 triplet pairing state that arises from a unique type of normal state will differ markedly from conventional, heavy fermion, or high temperature superconductors. Characteristics of such a state are outlined, and guidelines for making promising candidates are presented.

This is a figure of the spin density in the double perovskite structure compound La2VCuO6 ( postscript ) which illustrates how very different magnetic moments can be and still cancel exactly. In this figure, the surfaces shown are for a typical isosurface of the spin density of this ferrimagnet, which based on a local spin density functional calculation is an example of a half-metallic antiferromagnet. The Cu ion is the small, red-and-yellow surface, while the V ion is the large violet surface. The oxygen ions also have a net polarization, which appears as violet dumbbells between the Cu and V ions. There happen to be tiny red dots at the positions of the La ions. The color scheme (based on the magnitude of the gradient of the spin density) was chosen simply to emphasize the shape of the surfaces.

There is not yet any experimental confirmation about the possible half-metallic or antiferromagnetic nature of La2VCuO6, so the possibility of single spin superconductivity in this compound is highly speculative.