The puzzle of high-temperature superconductivity keeps getting hotter. First the cuprate superconductors were discovered, sporting layers of copper and oxygen atoms. A few months ago, a new class was discovered: the oxypnictides, with layers of iron and arsenic atoms. Both are layered compounds, with electrons moving in the two-dimensional planes. In both, the electrons acquire peculiar properties even at temperatures above the superconducting transition temperature. Why do these materials superconduct at relatively high temperatures? No one knows. Yet, recently Djordje Minic and Jean Heremans applied a space-time theory of extra dimensions - the Randall-Sundrum conjecture - to unsolved problems in superconductivity. In the work by Djordje Minic and Jean Heremans, the layered nature of the compounds is very important. According to the Randall-Sundrum scenario we live in a 3+1 dimensional space-time, where the force of gravity appears much weaker because our world is possibly just a boundary of a curved space-time with one extra spatial direction, making a 4+1 dimensional world. Similarly, one may envision that the two-dimensional electron planes in the high-temperature superconductors are 2+1 dimensional worlds and are the layers of an effectively curved space-time with one extra spatial direction, making a 3+1 dimensional world. The coupling between these planar electron worlds is captured by an effective Randall-Sundrum geometry of the resulting 3+1 dimensional space-time, which is responsible for the observed high superconducting temperatures and the unusual properties of the electrons at temperatures above the superconducting transition. In short, if the electrons in these materials were theoretical physicists, they would reach the conclusion that their planar world is just a boundary of an effectively curved space-time with one extra spatial dimension.

*featured in the August 16 issue of New Scientist magazine*