A new understanding of the physics of conductive materials has been uncovered by scientists observing the unusual movement of electrons in graphene.
Graphene is many times more conductive than copper thanks, in part, to its two-dimensional structure. In most metals, conductivity is limited by crystal imperfections which cause electrons to frequently scatter like billiard balls when they move through the material.
Now, observations in experiments at the National Graphene Institute have provided essential understanding as to the peculiar behaviour of electron flows in graphene, which need to be considered in the design of future Nano-electronic circuits.
In some high-quality materials, like graphene, electrons can travel micron distances without scattering, improving the conductivity by orders of magnitude. This so-called ballistic regime, imposes the maximum possible conductance for any normal metal, which is defined by the Landauer-Buttiker formalism.
Appearing today in Nature Physics, researchers at The University of Manchester, in collaboration with theoretical physicists led by Professor Marco Polini and Professor Leonid Levitov, show that Landauer’s fundamental limit can be breached in graphene. Even more fascinating is the mechanism responsible for this.
The new research demonstrates that this viscous fluid is even more conductive than ballistic electrons. The result is rather counter-intuitive, since typically scattering events act to lower the conductivity of a material, because they inhibit movement within the crystal. However, when electrons collide with each other, they start working together and ease current flow.
This happens because some electrons remain near the crystal edges, where momentum dissipation is highest, and move rather slowly. At the same time, they protect neighbouring electrons from colliding with those regions. Consequently, some electrons become super-ballistic as they are guided through the channel by their friends.
The researchers measured the resistance of graphene constrictions, and found it decreases upon increasing temperature, in contrast to the usual metallic behaviour expected for doped graphene.
By studying how the resistance across the constrictions changes with temperature, the scientists revealed a new physical quantity which they called the viscous conductance. The measurements allowed them to determine electron viscosity to such a high precision that the extracted values showed remarkable quantitative agreement with theory.
News Source: http://www.manchester.ac.uk/discover/news/electrons-flowing-like-liquid-in-graphene-start-a-new-wave-of-physics/
Know about graphene at http://www.news.qualitypointtech.com/know-about-graphene/
Emerging applications of Graphene:
Porous, 3-D forms of Graphene developed at MIT can be 10 times as strong as steel but much lighter
Graphene-coated solar panel generates Electricity from Rain Drops.
MIT discovers new way to turn Electricity into Light, using Graphene
Graphene Sieve turns Seawater into Drinking water
Watch more graphene videos at http://www.news.qualitypointtech.com/know-about-graphene/
