For many years, scientists have been trying to harness Bloch oscillations, an exotic kind of behavior by electrons that could introduce a new field of physics and important new technologies. Now, MIT physicists report on a new approach to achieving Bloch oscillations in recently introduced graphene superlattices. Graphene's electronic properties undergo an interesting transformation in the presence of an “electric mesh” (a periodic potential), resulting in new types of electron behavior not seen in pristine materials. In their recent work, the scientists show why graphene superlattices may be game changers in the pursuit of Bloch oscillations.
Normally, electrons exposed to a constant electric field accelerate in a straight line. However, Quantum Mechanics predicts that electrons in a crystal, or material composed of atoms arranged in an orderly fashion, can behave differently. Upon exposure to an electric field, they can oscillate in tiny waves—Bloch oscillations. “This surprising behavior is an iconic example of coherent dynamics in quantum many-body systems,” says Leonid Levitov, an MIT professor of physics and leader of the current work. Levitov is also affiliated with MIT’s Materials Research Laboratory.