Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A new kind of quantum bits in two dimensions

19.03.2018

Combining two ultra-thin material layers yields new possibilities for quantum electronics. A research team with members from TU Wien presents strongly tunable quantum systems.

Two novel materials, each composed of a single atomic layer and the tip of a scanning tunneling microscope - these are the ingredients to create a novel kind of a so-called "quantum dot". These extremely small nanostructures allow delicate control of individual electrons by fine-tuning their energy levels directly. Such devices are key for modern quantum technologies.


These are new kinds of quantum bits: extremely small nanostructures allow delicate control of individual electrons by fine-tuning their energy levels.

Credit: TU Wien


This is Florian Libisch.

Credit: TU Wien

The theoretical simulations for the new technology were performed in the team of Prof. Florian Libisch and Prof. Joachim Burgdörfer at TU Wien. The experiment involved the group of Prof. Markus Morgenstern at RWTH Aachen and the team around Nobel-prize laureates Andre Geim and Kostya Novoselov from Manchester who prepared the samples. The results have now been published in Nature Nanotechnology.

Tuning electron energies

„For many applications in the field of quantum technologies one requires a quantum system were electrons occupy two states - similar to a classical switch - on or off, with the difference that quantum physics also allows for arbitrary superpositions of the on and off states" explains Florian Libisch from the Institute for Theoretical Physics at TU Wien.

A key property of such systems is the energy difference between those two quantum states: "Efficiently manipulating the information stored in the quantum state of the electrons requires perfect control of the system parameters. An ideal system allows for continuous tuning the energy difference from zero to a large value" says Libisch.

For systems found in nature - for example atoms - this is usually difficult to realize. The energies of atomic states, and hence their differences, are fixed. Tuning energies becomes possible in synthetic nanostructures engineered towards confining electrons. Such structures are often referred to as quantum dots or "artificial atoms".

Two ultra-thin materials: graphene and hexagonal boron nitride

The international research team of TU Wien, RWTH Aachen and the University of Manchester now succeeded in developing a new type of quantum dots which allow for much more accurately and widely tunable energy levels of confined electrons than before. This progress was made possible by combining two very special materials: graphene, a conductive single atomic layer of carbon atoms, and hexagonal boron nitride, also a single layer of material quite similar to graphene except that it is insulating.

Exactly like graphene boron nitride also forms a honeycomb lattice. "The honeycombs in graphene and hexagonal boron nitride are, however, not exactly of equal size" explains Florian Libisch. "If you carefully put a single layer of graphene on top of hexagonal boron nitride, the layers cannot perfectly match. This slight mismatch creates a superstructure over distances of several nanometers, which results in an extremely regular wave-like spatial oscillation of the graphene layer out of the perfect plane."

As the extensive simulations at TU Wien show, exactly these oscillations in graphene on hexagonal boron nitride form the ideal scaffold to control electron energies. The potential landscape created by the regular superstructure allows for accurately placing the quantum dot, or even moving it continuously and thus smoothly changing its properties. Depending on the exact position of the tip of the scanning tunneling microscope, the energy levels of the electronic states inside the quantum dot change. "A shift by a few nanometers allows for changing the energy difference of two neighboring energy levels from minus five to plus ten millielectronvolts with high accuracy - a tuning range about fifty times larger than previously possible", explains Florian Libisch.

Towards „Valleytronics"

As a next step, the tip of the scanning tunneling microscope could be replaced by a series of nanoelectronic gates. This would allow for exploiting the quantum dot states of graphene on hexagonal boron nitride for scalable quantum technologies such as "valleytronics".

„This emerging new field is quickly becoming a center of attention", comments Florian Libisch. „There are multiple potential technological applications of these atomically thin materials - that is also why the TU Wien has also very recently established a special doctoral college focused on two-dimensional materials."

Contact:

Dr. Florian Libisch
Institut für Theoretische Physik
Technische Universität Wien
Wiedner Hauptstraße 8-10, 1040 Wien
T: +43-1-58801-13608
florian.libisch@tuwien.ac.at

Media Contact

Florian Aigner
florian.aigner@tuwien.ac
43-155-801-41027

 @tuvienna

http://www.tuwien.ac.at/tu_vienna/ 

Florian Aigner | EurekAlert!

More articles from Physics and Astronomy:

nachricht Weighing planets and asteroids
23.10.2018 | Max-Planck-Institut für Radioastronomie

nachricht Extremely Thin, Stable, and Bright: Materials for the Photonics of Tomorrow
23.10.2018 | Universität Bremen

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: memory-steel - a new material for the strengthening of buildings

A new building material developed at Empa is about to be launched on the market: "memory-steel" can not only be used to reinforce new, but also existing concrete structures. When the material is heated (one-time), prestressing occurs automatically. The Empa spin-off re-fer AG is now presenting the material with shape memory in a series of lectures.

So far, the steel reinforcements in concrete structures are mostly prestressed hydraulically. This re-quires ducts for guiding the tension cables, anchors for...

Im Focus: Goodbye, silicon? On the way to new electronic materials with metal-organic networks

Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz (Germany) together with scientists from Dresden, Leipzig, Sofia (Bulgaria) and Madrid (Spain) have now developed and characterized a novel, metal-organic material which displays electrical properties mimicking those of highly crystalline silicon. The material which can easily be fabricated at room temperature could serve as a replacement for expensive conventional inorganic materials used in optoelectronics.

Silicon, a so called semiconductor, is currently widely employed for the development of components such as solar cells, LEDs or computer chips. High purity...

Im Focus: Storage & Transport of highly volatile Gases made safer & cheaper by the use of “Kinetic Trapping"

Augsburg chemists present a new technology for compressing, storing and transporting highly volatile gases in porous frameworks/New prospects for gas-powered vehicles

Storage of highly volatile gases has always been a major technological challenge, not least for use in the automotive sector, for, for example, methane or...

Im Focus: Disrupting crystalline order to restore superfluidity

When we put water in a freezer, water molecules crystallize and form ice. This change from one phase of matter to another is called a phase transition. While this transition, and countless others that occur in nature, typically takes place at the same fixed conditions, such as the freezing point, one can ask how it can be influenced in a controlled way.

We are all familiar with such control of the freezing transition, as it is an essential ingredient in the art of making a sorbet or a slushy. To make a cold...

Im Focus: Micro energy harvesters for the Internet of Things

Fraunhofer IWS Dresden scientists print electronic layers with polymer ink

Thin organic layers provide machines and equipment with new functions. They enable, for example, tiny energy recuperators. In future, these will be installed...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

Conference to pave the way for new therapies

17.10.2018 | Event News

Berlin5GWeek: Private industrial networks and temporary 5G connectivity islands

16.10.2018 | Event News

 
Latest News

Weighing planets and asteroids

23.10.2018 | Physics and Astronomy

Fiber-based quantum communication - Interference of photons using remote sources

23.10.2018 | Information Technology

'Mushrooms' and 'brushes' help cancer-fighting nanoparticles survive in the body

23.10.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>