Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The fastest light-driven current source

26.09.2017

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job


Schematic of the experiment for ultra-fast current generation: When the light wave (red) hits the graphene (honeycomb grid), an electronic current is generated instantly.

Image: FAU / Takuya Higuchi

In gases, insulating materials and semiconductors, scientists have already shown that it is possible to steer electrons with light waves and thus, in principle, to control current. However, this concept has not yet been applied to metals as light cannot usually penetrate the material to control the electrons inside.

To avoid this effect, physicists in the working groups of Prof. Dr. Peter Hommelhoff and Prof. Dr. Heiko Weber used graphene – a semimetal consisting of only a single layer of carbon atoms. Even though graphene is an excellent conductor, it is thin enough to let some light penetrate the material and move the electrons.

For their experiments, the scientists fired extremely short laser pulses with specially engineered waveforms onto graphene. When these light waves hit the graphene, the electrons inside were hurled in one direction, like a whiplash.

‘Under intense optical fields, a current was generated within a fraction of an optical cycle – a half femtosecond. It was surprising that despite these enormous forces, quantum mechanics still plays a key role,’ explains Dr. Takuya Higuchi from the Chair of Laser Physics, the first author of the publication.

Two paths to the same destination

The researchers discovered that the current generation process in the graphene follows complicated quantum mechanics. The electrons travel from their initial state to the excited state by two paths rather than one – similar to a forked road leading to the same destination. Like a wave, the electrons can split at the fork and flow on both roads simultaneously. Depending on the relative phase between the split electron waves, when they meet again, the current can be very large, or not present at all.

‘This is like a water wave. Imagine a wave breaks against a building wall and flows to the left and the right of the building at the same time. At the end of the building, both parts meet again. If the partial waves meet at their peak, a very large wave results and current flows. If one wave is at its peak, the other at its lowest point, the two cancel one another out, and there is no current,’ explains Prof. Dr. Peter Hommelhoff from the Chair of Laser Physics. ‘We can use the light waves to regulate how the electrons move and how much electricity is generated.’

Will we see electronics controlled by light frequency in the future?

The results are another important step in bringing electronics and optics together. In the future, the method could open a door for realizing ultrafast electronics operating at optical frequencies.

The scientists have published their results, supported by the European Research Council (Consolidator Grant NearFieldAtto) and SFB 953 ‘Synthetic Carbon Allotropes', in the journal Nature: doi: 10.1038/nature23900

Further information:
Dr. Takuya Higuchi
Phone: +49 9131 8528335
takuya.higuchi@fau.de

Prof. Dr. Peter Hommelhoff
Phone: +49 9131 8527090
peter.hommelhoff@fau.de

Prof. Dr. Heiko Weber
Phone: +49 9131 8528421
heiko.weber@fau.de

Dr. Susanne Langer | idw - Informationsdienst Wissenschaft
Further information:
http://www.fau.de/

More articles from Physics and Astronomy:

nachricht Supercomputers without waste heat
07.12.2018 | Universität Konstanz

nachricht DF-PGT, now possible through massive sequencing techniques
06.12.2018 | Universitat Autonoma de Barcelona

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: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

Im Focus: Substitute for rare earth metal oxides

New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals

Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.

Im Focus: A bit of a stretch... material that thickens as it's pulled

Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.

Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...

Im Focus: The force of the vacuum

Scientists from the Theory Department of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science (CFEL) in Hamburg have shown through theoretical calculations and computer simulations that the force between electrons and lattice distortions in an atomically thin two-dimensional superconductor can be controlled with virtual photons. This could aid the development of new superconductors for energy-saving devices and many other technical applications.

The vacuum is not empty. It may sound like magic to laypeople but it has occupied physicists since the birth of quantum mechanics.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

Expert Panel on the Future of HPC in Engineering

03.12.2018 | Event News

Inaugural "Virtual World Tour" scheduled for december

28.11.2018 | Event News

 
Latest News

A new molecular player involved in T cell activation

07.12.2018 | Life Sciences

High-temperature electronics? That's hot

07.12.2018 | Materials Sciences

Supercomputers without waste heat

07.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>