For the first time ever, researchers have demonstrated that nano-sized graphene discs can absorb light in the infrared spectrum. Photo: DTU

Millions for research challenging the laws of physics

Monday 20 Feb 17
by Tom Nervil


Antti-Pekka Jauho
DTU Physics
+4545 25 63 35

The Danish National Research Foundation

Annually awards DKK 400 million (EUR 54 million) for research centres of the highest international calibre—so-called Centers of Excellence. This corresponds to approximately two per cent of total public research funding. The vision is to support and promote ground-breaking research—research that can make a difference to the way we think and live.

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Funding continues for Center for Nanostructures Graphene where research takes place on the nano scale, and new and surprising facts about the laws of physics come to light. 

Maxwell’s theory of electrodynamics is currently being challenged by researchers at DTU. At the Center for Nanostructured Graphene (CNG), researchers are gaining a deeper understanding of nanotechnology in line with technological advancements, and this basic research is now ensured through to 2022 thanks to funding from The Danish National Research Foundation.

The pioneering work seeks to explore the universe’s smallest elements and the meeting between classical electrodynamics and quantum physics. Søren-Peter Olesen, Director of The Danish National Research Foundation, fully expects the centre to continue delivering research of a high international calibre.

“In its first five years, the CNG has proven capable of establishing a basic research centre that can deliver the goods—and it has ambitious plans for the immediate future. For this reason, funding has been extended for a further four years. Being Denmark’s leading nanotechnology research centre simply is not enough—the centre must be capable of competing on the global stage. This is a clear criterion for receiving the funding, which can otherwise be spent as the centre best sees fit,” says Søren-Peter Olesen.

Thus, over the next few years, researchers from CNG have the opportunity to further challenge the theories regarding the nature of the universe at molecular and atomic level.

Centre Director Antti-Pekka Jauho, who is also a professor at DTU Nanotech, is naturally delighted.

“Over the next four years, we will be able to stack different 2D structures on top of each other to build completely new materials. The idea is the brainchild of 2010 Nobel Prize Laureates Andre Geim and Kostya Novoselov, but we have our own tricks and expertise, so I’m sure we will come up with some original systems.”

A very special material
CNG has brought together researchers from different disciplines to explore the myriad possibilities of graphene, which consists of carbon atoms bound together in a layer only a single atom thick. Graphene consists entirely of carbon atoms in a hexagonal lattice, giving the material some unique properties. For example, it is stronger than steel and a better electrical conductor than copper.

Despite being only an atom thick, it turns out that graphene can absorb up to 50 per cent of light at specific frequencies. However, such high absorption requires careful nanostructuring.

Most recently, researchers have demonstrated that graphene can also absorb light near the infrared spectrum if the flakes of nanostructured graphene can be rendered sufficiently small—i.e. approximately 10 nanometres in diameter. As well as possibly paving the way for a completely new range of optical structures and integrated optical circuits for telecommunications, this new knowledge also breaks with the previous understanding of graphene, light refraction, and the importance of size.

There is much evidence to suggest that understanding the structures’ optical properties will require more than classical insight. Once again, new research challenges the laws of physics, offering a new understanding of the structure of the universe at nano level. This kind of realisation is rarely coincidental.

Professor N. Asger Mortensen, who is affiliated with CNG, conducts research into the light’s interaction with nanostructures. For the past five years he has studied how graphene absorbs light.

“My initial interest was sparked when it became clear that graphene—which is only a single atom thick—could create shade, or absorb two per cent of the light. This was an entirely new discovery,” explains N. Asger Mortensen. The kind of discovery and curiosity that drives basic research. As early as 2014, N. Asger Mortensen succeeded in amending Maxwell’s more than 150-year-old equations and his use of Ohm’s law to describe electrodynamics in metallic nanostructures.

“We’re talking about corrections to classic electrodynamics, including some of the quantum mechanical effects that invariably come to light when dealing with ever smaller structures,” says N. Asger Mortensen.

Holes in the theory
Antti-Pekka Jauho points to the importance of a research centre being able to attract the best minds.

“The minute graphene discs are made by our own polymer chemists, whose existence and competences N. Asger Mortensen would have been unaware of without CNG. And the polymer chemists wouldn’t have known that their techniques could be used to nanostructure the graphene if I hadn’t asked them to join CNG back in 2010,” says Antti-Pekka Jauho.

With graphene discs measuring 18 nanometres in diameter, the material is thus able to absorb light close to the infra-red spectrum, but the experiments have also brought new challenges to the theoretical understanding—the classic descriptions can only partially explain the observed resonant frequencies. According to Antti-Pekka Jauho, it is this kind of discovery that drives further basic research.

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