Ultracold atom experiment finds collision-driven resistance hits a quantum cap

Researchers from the University of Toronto, L'École Normale Supérieure in Paris and Lehigh University found that collision-driven electrical resistance in an ultracold atomic system rises then levels off, ScienceDaily reported from University of Toronto materials on a Physical Review Letters study. The team studied potassium atoms cooled to nearly absolute zero in an optical lattice that mimics electrons moving through a solid. As collision frequency increased, resistance initially rose, then stopped climbing. Senior author Joseph Thywissen said electron-on-electron collisions are known to raise resistivity in some pure materials and that transmission lines can lose up to eight per cent of generated power as heat from resistance. Thywissen said the atoms, only a few nanometers in size, bumped into each other as if they were much larger, a quantum enhancement that makes on-site collisions more likely. Saturation of collision-driven resistivity suggests electron collisions in a metal may face a similar upper limit. The group said the results clarify how resistivity works in low-density metals and open paths to study strongly correlated atomic systems and quantum materials.