University of Southampton
In a metal, microscopically an electrical current is a stream of electrons flowing through a lattice of ions. As the electrons move, they bump into other electrons, the ions, and impurities. In conventional metals, like iron and lead, the interactions with other electrons and with ions are very weak: impurities are the biggest obstacles. These microscopic collisions produce a macroscopic frictional force, called resistance, which dissipates energy as heat and light. Anybody who ever used a toaster is familiar with the heat and light of resistance.
About 7% of the electrical power produced in the UK is lost as waste, due to resistance in power cables. The good news is that metals can become superconducting: their resistance can drop to zero, so that current flows without losing energy. If power cables were superconducting, power losses could be reduced by half! The bad news is that the highest temperature at which superconductivity occurs, in ceramics called cuprates, is around -140 C. Reaching -140 C requires liquid nitrogen, which makes superconducting power cables expensive.
The microscopic origin of cuprate superconductivity remains mysterious because the cuprates are unconventional metals: in the cuprates, the interactions between the electrons are strongest. In fact, the electrons batter each other about violently, producing a jumbled mess- a difficult problem indeed.
I study such systems using a technique called holography. In everyday life, a hologram is a two-dimensional image containing enough information to reconstruct a three-dimensional object. In theoretical physics, holography is the statement that some strongly-interacting systems are equivalent to Einstein's theory of gravity in one higher dimension. Using holography, I study many strongly -interacting systems, including the cuprates as well as collisions of atomic nuclei and insulators in magnetic fields. Holography may reveal the secret of cuprate superconductivity, and much more!
Interests and expertise (Subject groups)