Tao Jiang

Light passing through a thin crystal can change color and the direction of its oscillations. In a molybdenum disulfide flake just hundreds of atoms thick, an infrared beam turns green, and its polarization, the way the light wave oscillates, obeys the crystal's geometry.

Ordinary window glass may seem frozen forever, but inside, atoms never stay still. In amorphous germanium telluride (GeTe)—a material used in rewritable discs and non-volatile memory — physicists have for the first time directly tracked how atomic bonds stretch and bend in trillionths of a second.