Physicists Localize 3-D Matter Waves For First Time

University of Illinois physicists have experimentally demonstrated for the first time how three-dimensional conduction is affected by the defects that plague materials. Understanding these effects is important for many electronics applications. Led by physics professor Brian DeMarco, the researchers achieved complete localization of quantum matter waves in three dimensions, first theorized roughly half a century ago. The group published its findings in the Oct. 7 issue of the journal Science.

Defects in materials are inevitable, but their effects are poorly understood. Understanding how disorder in a material affects waves traveling through it has implications for many applications, including ultrasonic waves in medical imaging, lasers for imaging and sensing, and electron waves for electronics and superconductors.

"The physics behind disorder is fundamental to understanding the impact of unavoidable material imperfections on these kinds of applications," DeMarco said.

Scientists have long theorized, but never observed, that strong disorder causing interference on all sides can trap a matter wave in one place, a phenomenon known as Anderson localization.

According to DeMarco, this is analogous to a trumpeter playing in a concert hall filled with randomly placed barriers that reflect sound waves. Instead of traveling in all directions, the sound stays at its source, never propagating outward because of destructive interference.

"The result? Perfect silence everywhere in the concert hall. The trumpeter blows into his instrument, but the sound never leaves the trumpet," DeMarco said. "That's exactly the case in our experiment, although we use quantum matter waves instead of sound, and the barriers are created using a speckled green laser beam."