“The ability to manipulate electrons in a conducting material like light rays opens up entirely new ways of thinking about electronics,” explained Cory Dean, assistant professor at Columbia University. “For example, the switches that make up computer chips operate by turning the entire device on or off, and this consumes significant power. Using lensing to steer an electron ‘beam’ between electrodes could be more efficient, solving one of the critical bottlenecks to achieving faster and more energy efficient electronics.”
“Electron lensing could enable on-chip versions of an electron microscope, with the ability to perform atomic scale imaging and diagnostics. Other components inspired by optics, such as beam splitters and interferometers, could enable new studies of the quantum nature of electrons in the solid state,” Dean added.
According to the researchers, electrons travelling through pure conductors can travel in straight lines like light rays, enabling optics-like phenomena to emerge. In materials, the electron density plays a similar role to the index of refraction, and electrons refract when they pass from a region of one density to another.
The development of two-dimensional conducting layers in high-purity semiconductors such as Gallium arsenide allowed researchers to first demonstrate electron optics, including the effects of both refraction and lensing. However, in these materials, electrons only travelled without scattering at low temperatures, limiting technological applications. The presence of an energy gap between the conduction and valence band also scattered electrons at interfaces and prevented observation of negative refraction in semiconductor p-n junctions. In this study, graphene overcame both these limitations.
“In many ways, this intensity of transmission is a more crucial parameter,” said Avik Ghosh, professor at the University of Virginia. “It determines the probability that electrons actually make it past the barrier, rather than just their refracted angles. The transmission determines many of the performance metrics for devices based on these effects, such as the on-off ratio in a switch.”
