Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New quantum phenomena in graphene superlattices

19.09.2017

A team of Graphene Flagship researchers led by the University of Manchester reported in the journal Science showing the first new type of quantum oscillation to be reported for thirty years. This occurs by applying a magnetic field and it is the first of its kind to be present at high temperature and on the mesoscale. This research also sheds light on the Hofstadter butterfly phenomenon.

Quantum theory is the study of physics at the atomic and sub atomic level. It quantises energy and momentum and shows how objects are characterised as both particles and waves. Quantum oscillations can be used to map the properties of new materials in the presence of a magnetic field.


This is an example of the Hofstadter butterfly phenomenon.

Credit: The University of Manchester

This paper shows how it is possible to tune the magnetic field applied to a heterostructure comprising of graphene and boron nitride to create a whole host of different electronic materials.

The superlattice, created in graphene by its exact placement with regards to a periodically arranged boron nitride layer, interacts with the magnetic field in such a way that it is possible to tune its oscillation to manufacture bands and gaps in its electronics structure - meaning that the magnetic field can be used to tune the materials to be metallic, semiconducting or conducting.

Andre Geim, a leading member of the team and the 2010 Nobel Laureate, says "Oscillatory quantum effects always present milestones in our understanding of materials properties. They are exceedingly rare. It is more than 30 years since a new type of quantum oscillation was reported." He added "Our oscillations stand out by their extreme robustness, happening under ambient conditions in easily accessible magnetic fields."

This work also sheds further light on Hofstadter's butterfly, a fractal pattern that describes the behaviour of electrons in a magnetic field, measured experimentally for the first time in 2013 using a graphene and boron-nitride heterostructure. In the original theoretical work on which Hofstadter's butterfly is based the electrons modelled to create the fractal pattern were treated as Bloch electrons (electrons that do not interact with one another and move within a periodic electric potential within a lattice). The research shown here illustrates how these complex fractal patterns can be viewed as Langmuir quantisation which is the quantisation of cyclotron orbits (taking what is normally thought of as a circular orbit and instead viewing it as linear)

Professor Vladimir Falko, Director of the National Graphene Institute commented "Our work helps to demystify the Hofstadter butterfly. The complex fractal structure of the Hofstadter butterfly spectrum can be understood as simple Landau quantisation in the sequence of new metals created by magnetic field."

Professor Bart van Wees, Head of the Physics of Nanodevices group at the Zernike Institute for Advanced Materials, Groningen, The Netherlands added "We have always considered quantum oscillations as very brittle, easily destroyed at higher temperatures but the authors have shown that these can now be observed at room temperature, or even higher. This is good news for possible new applications of these and other systems which are based on Van der Waals stacking of two-dimensional materials."

Media Contact

Sian Fogden
comms@graphene.cam.ac.uk
44-012-237-62418

 @GrapheneCA

http://graphene-flagship.eu 

Sian Fogden | EurekAlert!
Further information:
https://graphene-flagship.eu/new-quantum-phenomena-in-graphene-superlattices

More articles from Physics and Astronomy:

nachricht A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

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: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>