High-temperature superconductivity emerges in the copper oxide compounds on changing the electron density of an insulator in which the electron spins are antiferromagnetically ordered. A key characteristic of the superconductor is that electrons can be extracted from it at zero energy only if their momenta take one of four specific values (the ?nodal points?). A central enigma has been the evolution of those zero-energy electrons in the metallic state between the antiferromagnet and the superconductor, and recent experiments yield apparently contradictory results. The oscillation of the resistance in this metal as a function of magnetic field indicates that the zero-energy electrons carry momenta that lie on elliptical ?Fermi pockets?, whereas ejection of electrons by high-intensity light indicates that the zero-energy electrons have momenta only along arc-like regions, or ?Fermi arcs?. We present a theory of new states of matter, which we call ?algebraic charge liquids?, and which arise naturally between the antiferromagnet and the superconductor, and reconcile these observations. Our theory also explains a puzzling dependence of the density of superconducting electrons on the total electron density, and makes a number of unique predictions for future experiments.
The historic takeover of Fannie Mae and Freddie Mac, which could come as soon as this weekend, moved to the forefront of the presidential campaign Saturday.
In the arena that night, the whole last minute was drowned out by cheers — and then when the soaring music swelled, the confetti rained down as the harbinger of balloons and the hopeful first family took the stage, forget about it — it was a perfect end to a convention that last Monday, no one even knew if it would happen. But it did, and I'm so glad to have been there.
