K. W. West

Imagine a superhighway where cars zoom along with barely a slowdown: that's what a layer of ultraclean semiconductor looks like, where electrons travel vast distances without a single collision. Scientists have built a transistor in which electrons run twice as fast as in any similar device before.

A layer of electrons trapped between two semiconductor plates lines up into a neat lattice at low temperatures, like beads on a string stretched between your fingers. As the temperature rises, order collapses: the crystal melts. But exactly how it melts has long been a puzzle.

Electrons in an ultra-clean gallium arsenide film behave like a crowd at a crossroads, where the tilt of the magnetic field sets the direction. At zero tilt, they form a compressible liquid of composite fermions, particles made of an electron and a pair of vortices.