Two-dimensional electron liquids
Truly two-dimensional objects are rare. Even a thin piece of paper is trillions of atoms thick. When physicists do succeed in producing 2D systems, quantum interactions can lead to new phenomena and Nobel prizes. Two examples: graphene---single-atom-thick sheets of carbon atoms---has unique mechanical, electrical, and optical properties; and two-dimensional electron gases (2DEG)---planar collections of electrons supported at the interface between certain semiconductors such as gallium arsenide---allow the observation of such emergent behaviors as the quantum Hall eff