Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Light from exotic particle states

16.04.2019

A new type of light-emitting diode has been developed at TU Wien. Light is produced from the radiative decay of exciton complexes in layers of just a few atoms thickness.

When particles bond in free space, they normally create atoms or molecules. However, much more exotic bonding states can be produced inside solid objects.


Short electric pulses are sent through a system of ultra thin layers, which then emits light.

Credit: TU Wien

Researchers at TU Wien have now managed to utilise this: so-called "multi-particle exciton complexes" have been produced by applying electrical pulses to extremely thin layers of material made from tungsten and selenium or sulphur. These exciton clusters are bonding states made up of electrons and "holes" in the material and can be converted into light.

The result is an innovative form of light-emitting diode in which the wavelength of the desired light can be controlled with high precision. These findings have now been published in the journal "Nature Communications".

Electrons and holes

In a semiconductor material, electrical charge can be transported in two different ways. On the one hand, electrons can move straight through the material from atom to atom in which case they take negative charge with them. On the other hand, if an electron is missing somewhere in the semiconductor that point will be positively charged and referred to as a "hole".

If an electron moves up from a neighbouring atom and fills the hole, it in turn leaves a hole in its previous position. That way, holes can move through the material in a similar manner to electrons but in the opposite direction.

"Under certain circumstances, holes and electrons can bond to each other", says Prof. Thomas Mueller from the Photonics Institute (Faculty of Electrical Engineering and Information Technology) at TU Wien. "Similar to how an electron orbits the positively charged atomic nucleus in a hydrogen atom, an electron can orbit the positively charged hole in a solid object."

Even more complex bonding states are possible: so-called trions, biexcitons or quintons which involve three, four or five bonding partners. "For example, the biexciton is the exciton equivalent of the hydrogen molecule H2", explains Thomas Mueller.

Two-dimensional layers

In most solids, such bonding states are only possible at extremely low temperatures. However the situation is different with so-called "two-dimensional materials", which consist only of atom-thin layers. The team at TU Wien, whose members also included Matthias Paur and Aday Molina-Mendoza, has created a cleverly designed sandwich structure in which a thin layer of tungsten diselenide or tungsten disulphide is locked in between two boron nitride layers. An electrical charge can be applied to this ultra-thin layer system with the help of graphene electrodes.

"The excitons have a much higher bonding energy in two-dimensional layered systems than in conventional solids and are therefore considerably more stable. Simple bonding states consisting of electrons and holes can be demonstrated even at room temperature. Large, exciton complexes can be detected at low temperatures", reports Thomas Mueller. Different excitons complexes can be produced depending on how the system is supplied with electrical energy using short voltage pulses. When these complexes decay, they release energy in the form of light which is how the newly developed layer system works as a light-emitting diode.

"Our luminous layer system not only represents a great opportunity to study excitons, but is also an innovative light source", says Matthias Paur, lead author of the study. "We therefore now have a light-emitting diode whose wavelength can be specifically influenced - and very easily too, simply via changing the shape of the electrical pulse applied."

###

Contact:

Prof. Thomas Mueller
Photonics Institute
TU Wien
Tel.: +43 (0)1 58801 38739
thomas.mueller@tuwien.ac.at

Media Contact

Florian Aigner
florian.aigner@tuwien.ac.at
43-158-801-41027

 @tuvienna

http://www.tuwien.ac.at/tu_vienna/

Prof. Thomas Mueller | EurekAlert!
Further information:
http://dx.doi.org/10.1038/s41467-019-09781-y

More articles from Physics and Astronomy:

nachricht Hubble discovers mysterious black hole disc
12.07.2019 | ESA/Hubble Information Centre

nachricht What happens when you explode a chemical bond?
12.07.2019 | University of California - Berkeley

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: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

Im Focus: Modelling leads to the optimum size for platinum fuel cell catalysts: Activity of fuel cell catalysts doubled

An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...

Im Focus: The secret of mushroom colors

Mushrooms: Darker fruiting bodies in cold climates

The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...

Im Focus: First results of the new Alphatrap experiment

Physicists at the Max Planck Institute for Nuclear Physics in Heidelberg report the first result of the new Alphatrap experiment. They measured the bound-electron g-factor of highly charged (boron-like) argon ions with unprecedented precision of 9 digits. In comparison with a new highly accurate quantum electrodynamic calculation they found an excellent agreement on a level of 7 digits. This paves the way for sensitive tests of QED in strong fields like precision measurements of the fine structure constant α as well as the detection of possible signatures of new physics. [Physical Review Letters, 27 June 2019]

Quantum electrodynamics (QED) describes the interaction of charged particles with electromagnetic fields and is the most precisely tested physical theory. It...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

A human liver cell atlas

15.07.2019 | Life Sciences

No more trial-and-error when choosing an electrolyte for metal-air batteries

15.07.2019 | Power and Electrical Engineering

Possibilities of the biosimilar principle of learning are shown for a memristor-based neural network

15.07.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>