Rutgers physicists discover novel electronic properties in two-dimensional carbon structure
Previously predicted but unobserved interactions between massless particles may lead to speedy, powerful electronic devices
NEW BRUNSWICK, N.J. – Rutgers researchers have discovered novel electronic properties in two-dimensional sheets of carbon atoms called graphene that could one day be the heart of speedy and powerful electronic devices.
The new findings, previously considered possible by physicists but only now being seen in the laboratory, show that electrons in graphene can interact strongly with each other. The behavior is similar to superconductivity observed in some metals and complex materials, marked by the flow of electric current with no resistance and other unusual but potentially useful properties. In graphene, this behavior results in a new liquid-like phase of matter consisting of fractionally charged quasi-particles, in which charge is transported with no dissipation.
In a paper issued online by the prestigious science journal Nature and slated for print publication in the coming weeks, physics professor Eva Andrei and her Rutgers colleagues note that the strong interaction between electrons, also called correlated behavior, had not been observed in graphene in spite of many attempts to coax it out. This led some scientists to question whether correlated behavior could even be possible in graphene, where the electrons are massless (ultra-relativistic) particles like photons and neutrinos. In most materials, electrons are particles that have mass.
"Our work demonstrated that earlier failures to observe correlated behavior were not due to the physical nature of graphene," said Eva Andrei, physics professor in the Rutgers School of Arts and Sciences. "Rather, it was because of interference from the material which supported graphene samples and the type of electrical probes used to study it."
This finding should encourage scientists to further pursue graphene and related materials for future electronic applications, including replacements for today's silicon-based semiconductor materials. Industry experts expect silicon technology to reach fundamental performance limits in a little more than a decade.
The Rutgers physicists further describe how they observed the collective behavior of the ultra-relativistic charge carriers in graphene through a phenomenon known as the fractional quantum Hall effect (FQHE). The FQHE is seen when charge carriers are confined to moving in a two-dimensional plane and are subject to a perpendicular magnetic field. When interactions between these charge carriers are sufficiently strong they form new quasi-particles with a fraction of an electron's elementary charge. The FHQE is the quintessential signature of strongly correlated behavior among charge-carrying particles in two dimensions.
The FHQE is known to exist in semiconductor-based, two-dimensional electron systems, where the electrons are massive particles that obey conventional dynamics versus the relativistic dynamics of massless particles. However, it was not obvious until now that ultra-relativistic electrons in graphene would be capable of exhibiting collective phenomena that give rise to the FHQE. The Rutgers physicists were surprised that the FHQE in graphene is even more robust than in standard semiconductors.
