Tracking down nano-size current loops using polarized neutrons

Determining the origin of high-temperature superconductivity is probably the single most important challenge faced today by solid-state physicists. This despite 30 years of extensive research efforts. High temperature superconductors are actually rather bad electrical conductors at room temperature. If they are cooled, they form a so-called "pseudogap phase" where electricity is conducted in a rather peculiar manner, with preferential directions. When cooled further, to temperatures easily reach...