Electron pairing against the odds

A principle of basic physics holds that similarly charged particles repel each other, but in solids the unthinkable is possible: electrons can get together. When mediated by the right sort of lattice vibrations, electrons can overcome their repulsion and form bound pairs, a well-known effect that can lead to superconductivity. Shahal Ilani and colleagues engineer an even more exotic effect of mutual electron attraction, mediated by other electrons. They accomplish this by placing two carbon nanotube electronic devices next to each other with high, submicrometre precision. The repulsion between the electrons confined in small area in one nanotube can be turned into attraction by accurately placing and tuning the other nanotube. This work resolves a long-standing fundamental question of whether electronic electron pairing is possible and provides a novel platform for quantum electronic devices.