Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New study confirms exotic electric properties of graphene

19.11.2009
First, it was the soccer-ball-shaped molecules dubbed buckyballs. Then it was the cylindrically shaped nanotubes. Now, the hottest new material in physics and nanotechnology is graphene: a remarkably flat molecule made of carbon atoms arranged in hexagonal rings much like molecular chicken wire.

Not only is this the thinnest material possible, but it also is 10 times stronger than steel and it conducts electricity better than any other known material at room temperature. These and graphene's other exotic properties have attracted the interest of physicists, who want to study them, and nanotechnologists, who want to exploit them to make novel electrical and mechanical devices.

"There are two features that make graphene exceptional," says Kirill Bolotin, who has just joined the Vanderbilt Department of Physics and Astronomy as an assistant professor. "First, its molecular structure is so resistant to defects that researchers have had to hand-make them to study what effects they have. Second, the electrons that carry electrical charge travel much faster and generally behave as if they have far less mass than they do in ordinary metals or superconductors."

Bolotin has been directly involved in the efforts to manufacture and characterize this exotic new material as a post-doctoral fellow in the laboratory of Philip Kim at Columbia University. In a paper published last week in the journal Nature, he and his Columbia colleagues report that they have managed to clean up graphene enough so that it exhibits a bizarre electrical phenomenon called the fractional quantum Hall effect, where the electrons act together to create new particles with electrical charges that are a fraction that of individual electrons.

Although graphene is the first truly two-dimensional crystalline material that has been discovered, over the years scientists have put considerable thought into how two-dimensional gases and solids should behave. They have also succeeded in creating a close approximation to a two-dimensional electron gas by bonding two slightly different semiconductors together. Electrons are confined to the interface between the two and their motions are restrained to two dimensions. When such a system is cooled down to less than one degree above absolute zero and a strong magnetic field is applied, then the fractional quantum Hall effect appears.

Since scientists figured out how to make graphene five years ago, they have been trying to get it to exhibit this effect with only marginal success. According to Bolotin, the Columbia group figured out that interference from the surface the graphene was sitting on was the problem. So they applied semiconductor lithography techniques to suspend ultraclean graphene sheets between microscopic posts above the surface of semiconductor chips. When they cooled this configuration down within six degrees of absolute zero and applied a magnetic field, the graphene generated a robust quantum Hall effect as predicted by theory.

The best way to understand this counterintuitive effect is to think of the electrons in graphene as a forming a (very thin) sea of charge. When the magnetic field is applied, it generates whirlpools in the electron fluid. Because electrons carry a negative charge, these vortices have a positive charge. They form with fractional charges such as one-third, one-half and two-thirds that of an electron. These positive charge carriers are attracted to and attach to the conduction electrons, creating quasi-particles with fractional charges.

Understanding the electrical properties of graphene is important because, unlike the other materials used by the electronics industry, it remains stable and conductive down to the molecular scale. As a result, when the current silicon technology reaches it's a fundamental miniaturization limit in coming years, graphene could very well take its place.

Meanwhile, some theoretical physicists are interested in graphene for a totally different reason: It provides a new way to test their theories.

As electrons move through ordinary metals, they interact with the electrical fields produced by the lattice of metal atoms, which push and pull them in a complex fashion. The net result is that the electrons act as if they have a mass different from that of ordinary electrons. So physicists call this an "effective mass" and consider them to be quasiparticles. When traveling through graphene they also act as quasiparticles, but they behave as if they have a mass of zero. It turns out that graphene quasiparticles, unlike those in other materials, obey the rules of quantum electrodynamics, the same relativistic equations that physicists use to describe the behavior of particles in black holes and high-energy particle accelerators. As a result, this new material may allow physicists to conduct tabletop experiments that test their theoretical models of some of the most extreme environments in the universe.

The research was supported by grants from Microsoft Project Q, the Defense Advanced Research Project Agency and the Department of Energy.

[Note: A multimedia version of this story is available on Exploration, Vanderbilt's online research magazine, at http://www.vanderbilt.edu/exploration/stories/graphene.html]

David F. Salisbury | EurekAlert!
Further information:
http://www.vanderbilt.edu

More articles from Physics and Astronomy:

nachricht Applicability of dynamic facilitation theory to binary hard disk systems
08.12.2016 | Nagoya Institute of Technology

nachricht Will Earth still exist 5 billion years from now?
08.12.2016 | KU Leuven

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>