Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Graphene: A quantum of current - When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene

Electron wave passing through a narrow constriction.
CREDIT: TU Wien
Electron wave passing through a narrow constriction.

CREDIT: TU Wien

Abstract:
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms arranged in a honeycomb lattice. But graphene research did not stop there. New interesting properties of this material are still being found. An international team of researchers has now explained the peculiar behaviour of electrons moving through narrow constrictions in a graphene layer. The results have been published in the journal Nature Communications.

Graphene: A quantum of current - When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene

Vienna, Austria | Posted on May 20th, 2016

The Electron is a Wave

"When electrical current flows through graphene, we should not imagine the electrons as little balls rolling through the material", says Florian Libisch from TU Wien (Vienna), who led the theoretical part of the research project. The electrons swash through the graphene as a long wave front, the wavelength can be a hundred times larger than the space between two adjacent carbon atoms. "The electron is not confined to one particular carbon atom, in some sense it is located everywhere at the same time", says Libisch.

The team studied the behaviour of electrons squeezing through a narrow constriction in a graphene sheet. "The wider the constriction, the larger the electron flux - but as it turns out, the relationship between the width of the constriction, the energy of the electrons and the electric current is quite complex", says Florian Libisch. "When we make the constriction wider, the electric current does not increase gradually, it jumps at certain points. This is a clear indication of quantum effects."

If the wavelength of the electron is so large that it does not fit through the constriction, the electron flux is very low. "When the energy of the electron is increased, its wavelength decreases", explains Libisch. "At some point, one wavelength fits through the constriction, then two wavelengths, then three - this way the electron flux increases in characteristic steps." The electric current is not a continuous quantity, it is quantized.

Theory and Experiment

This effect can also be observed in other materials. Detecting it in graphene was much more difficult, because its complex electronic properties lead to a multitude of additional effects, interfering with each other. The experiments were performed at the group of Christoph Stampfer at the RWTH Aachen (Germany), theoretical calculations and computer simulations were performed in Vienna by Larisa Chizhova and Florian Libisch at the group of Joachim Burgdörfer.

For the experiments, the graphene sheets hat to be etched into shape with nanometre precision. "Protecting the graphene layer by sandwiching it between atomic layers of hexagonal boron nitride is critical for demonstrating the quantized nature of current in graphene" explains Christoph Stampfer. Current through the devices is then measured at extremely low temperatures. "We use liquid helium to cool our samples, otherwise the fragile quantum effects are washed out by thermal fluctuations" says Stampfer. Simulating the experiment poses just as much of a challenge. "A freely moving electron in the graphene sheet can occupy as many quantum states as there are carbon atoms", says Florian Libisch, "more than ten million, in our case." This makes the calculations extremely demanding. An electron in a hydrogen atom can be described using just a few quantum states. The team at TU Wien (Vienna) developed a large scale computer simulation and calculated the behaviour of the electrons in graphene on the Vienna Scientific Cluster VSC, using hundreds of processor cores in parallel.

Edge States

As it turns out, the edge of the graphene sheet plays a crucial role. "As the atoms are arranged in a hexagonal pattern, the edge can never be a completely straight line. On an atomic scale, the edge is always jagged", says Florian Libisch. In these regions, the electrons can occupy special edge states, which have an important influence on the electronic properties of the material. "Only with large scale computer simulations using the most powerful scientific computer clusters available today, we can find out how these edge states affect the electrical current", says Libisch. "The excellent agreement between the experimental results and our theoretical calculations shows that we have been very successful."

The discovery of graphene opened the door to a new research area: ultrathin materials which only consist of very few atomic layers are attracting a lot of attention. Especially the combination of graphene and other materials - such as boron nitride, as in this case - is expected to yield interesting results. "One thing is for sure: whoever wants to understand tomorrow's electronics has to know a lot about quantum physics", says Florian Libisch.

####

For more information, please click here

Contacts:
Florian Aigner

43-158-801-41027

Further information:
Dr. Florian Libisch
Institute for Theoretical Physics
TU Wien
Wiedner Hauptstraße 8-10, 1040 Wien
T: +43-1-58801-13608

Copyright © Vienna University of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Original publication: "Size quantization of Dirac fermions in graphene constrictions", Nature Communications, DOI: 10.1038/NCOMMS11528:

Related News Press

News and information

Virginia Tech physicists propose path to faster, more flexible robots: Virginia Tech physicists revealed a microscopic phenomenon that could greatly improve the performance of soft devices, such as agile flexible robots or microscopic capsules for drug delivery May 17th, 2024

Gene therapy relieves back pain, repairs damaged disc in mice: Study suggests nanocarriers loaded with DNA could replace opioids May 17th, 2024

Shedding light on perovskite hydrides using a new deposition technique: Researchers develop a methodology to grow single-crystal perovskite hydrides, enabling accurate hydride conductivity measurements May 17th, 2024

What is "time" for quantum particles? Publication by TU Darmstadt researchers in renowned journal "Science Advances" May 17th, 2024

Quantum Physics

Finding quantum order in chaos May 17th, 2024

International research team uses wavefunction matching to solve quantum many-body problems: New approach makes calculations with realistic interactions possible May 17th, 2024

What is "time" for quantum particles? Publication by TU Darmstadt researchers in renowned journal "Science Advances" May 17th, 2024

Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024

2 Dimensional Materials

Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in cuprate superconductor May 17th, 2024

First human trial shows ‘wonder’ material can be developed safely: A revolutionary nanomaterial with huge potential to tackle multiple global challenges could be developed further without acute risk to human health, research suggests February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Thin films

Utilizing palladium for addressing contact issues of buried oxide thin film transistors April 5th, 2024

Graphene/ Graphite

First human trial shows ‘wonder’ material can be developed safely: A revolutionary nanomaterial with huge potential to tackle multiple global challenges could be developed further without acute risk to human health, research suggests February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Possible Futures

Advances in priming B cell immunity against HIV pave the way to future HIV vaccines, shows quartet of new studies May 17th, 2024

International research team uses wavefunction matching to solve quantum many-body problems: New approach makes calculations with realistic interactions possible May 17th, 2024

Aston University researcher receives £1 million grant to revolutionize miniature optical devices May 17th, 2024

Gene therapy relieves back pain, repairs damaged disc in mice: Study suggests nanocarriers loaded with DNA could replace opioids May 17th, 2024

Chip Technology

Diamond glitter: A play of colors with artificial DNA crystals May 17th, 2024

Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in cuprate superconductor May 17th, 2024

Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024

Utilizing palladium for addressing contact issues of buried oxide thin film transistors April 5th, 2024

Nanoelectronics

Interdisciplinary: Rice team tackles the future of semiconductors Multiferroics could be the key to ultralow-energy computing October 6th, 2023

Key element for a scalable quantum computer: Physicists from Forschungszentrum Jülich and RWTH Aachen University demonstrate electron transport on a quantum chip September 23rd, 2022

Reduced power consumption in semiconductor devices September 23rd, 2022

Atomic level deposition to extend Moore’s law and beyond July 15th, 2022

Discoveries

Virginia Tech physicists propose path to faster, more flexible robots: Virginia Tech physicists revealed a microscopic phenomenon that could greatly improve the performance of soft devices, such as agile flexible robots or microscopic capsules for drug delivery May 17th, 2024

Diamond glitter: A play of colors with artificial DNA crystals May 17th, 2024

Finding quantum order in chaos May 17th, 2024

Advances in priming B cell immunity against HIV pave the way to future HIV vaccines, shows quartet of new studies May 17th, 2024

Materials/Metamaterials/Magnetoresistance

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Focused ion beam technology: A single tool for a wide range of applications January 12th, 2024

Catalytic combo converts CO2 to solid carbon nanofibers: Tandem electrocatalytic-thermocatalytic conversion could help offset emissions of potent greenhouse gas by locking carbon away in a useful material January 12th, 2024

Announcements

Virginia Tech physicists propose path to faster, more flexible robots: Virginia Tech physicists revealed a microscopic phenomenon that could greatly improve the performance of soft devices, such as agile flexible robots or microscopic capsules for drug delivery May 17th, 2024

Diamond glitter: A play of colors with artificial DNA crystals May 17th, 2024

Finding quantum order in chaos May 17th, 2024

Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in cuprate superconductor May 17th, 2024

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

International research team uses wavefunction matching to solve quantum many-body problems: New approach makes calculations with realistic interactions possible May 17th, 2024

Gene therapy relieves back pain, repairs damaged disc in mice: Study suggests nanocarriers loaded with DNA could replace opioids May 17th, 2024

Shedding light on perovskite hydrides using a new deposition technique: Researchers develop a methodology to grow single-crystal perovskite hydrides, enabling accurate hydride conductivity measurements May 17th, 2024

Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in cuprate superconductor May 17th, 2024

Quantum nanoscience

What is "time" for quantum particles? Publication by TU Darmstadt researchers in renowned journal "Science Advances" May 17th, 2024

Simulating magnetization in a Heisenberg quantum spin chain April 5th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Bridging light and electrons January 12th, 2024

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project