Electrons conduct electricity like bouncing balls in Graphene ‘billiards table’

Washington, Sept 16: Physicists at the University of California, Riverside have found that electrons conduct electricity in Graphene the same way balls bounce back from the walls of a billiards table.

Graphene is a two-dimensional honeycomb lattice of carbon atoms, and, structurally, is related to carbon nanotubes (tiny hollow tubes formed by rolling up sheets of graphene) and buckyballs (hollow carbon molecules that form a closed cage).

Electrons encounter little or no obstacle in the hexagonal-ring structure of carbon atoms in graphene, where they roam about freely, conducting electric charge with extremely low resistance.

The research team, led by Chun Ning (Jeanie) Lau, found that the electrons in graphene are reflected back by the only obstacle they meet, the graphene’s boundaries.

“These electrons meet no other obstacles and behave like quantum billiard balls. They display properties that resemble both particles and waves,” said Lau, an assistant professor who joined UCR’s Department of Physics and Astronomy in 2004.

Prof. Lau observed that when the electrons are reflected from one of the boundaries of graphene, the original and reflected components of the electron can interfere with each other, the way outgoing ripples in a pond might interfere with ripples reflected back from the banks.

Her lab detected the “electronic interference” by measuring graphene’s electrical conductivity at extremely low (0.26 Kelvin) temperatures. She said that at such low temperatures the quantum properties of electrons could be studied more easily.

“We found that the electrons in graphene could display wave-like properties, which could lead to interesting applications such as ballistic transistors, which is a new type of transistor, as well as resonant cavities for electrons,” said Prof. Lau.

In their experiments, Prof. Lau and her students first peeled off a single sheet of graphene from graphite, a layered structure consisting of rings of six carbon atoms arranged in stacked horizontal sheets.

Next, the researchers attached nanoscale electrodes to the graphene sheet, which they then refrigerated in a cooling device. Finally, they measured the electrical conductivity of the graphene sheet.

Prof. Lau said the findings underscored graphene’s potential for new kinds of transistors based on quantum physics, adding that it has good potential to replace silicon as conductors in electronic materials. (With Inputs from ANI)