Graphene membranes’ anomalous dynamics

The burgeoning exploration and development of the nanoworld is forcing scientists to reexamine and reframe many established aspects of our familiar macroscopic world. Among the tenets experiencing renewed interest is the nature of the thermal fluctuations that underlie the random walks of Brownian motion (see, for example, the Quick Study by Mark Raizen and Tongcang Li, Physics Today, January 2015, page 56). The University of Arkansas’s Paul Thibado and colleagues now report ultraprecise dynamical measurements on a freestanding, atomically thin sheet of graphene that show clear deviations from classical Brownian behavior. With its regular hexagonal lattice, monolayer graphene offers an exceptionally clean two-dimensional system for studying membrane behavior. Using a custom scanning tunneling microscope (STM), the researchers tracked the out-of-plane dynamics of an atom-sized region of the membrane with subnanometer, millisecond resolution for more than two and a half hours. Over that time, the region’s height exhibited Brownian...