Electron correlations in carbon nanostructures

December 03, 2019

New materials are needed to further reduce the size of electronic components and thus make devices such as laptops and smartphones faster and more efficient. Tiny nanostructures of the novel material graphene are promising in this respect. Graphene consists of a single layer of carbon atoms and, among other things, has a very high electrical conductivity. However, the extreme spatial confinement in such nanostructures influences strongly their electronic properties. A team led by Professor Michael Bonitz of the Institute for Theoretical Physics and Astrophysics (ITAP) at Kiel University has now succeeded in simulating the detailed behavior of electrons in these special nanostructures using an elaborate computational model. This knowledge is crucial for the potential use of graphene nanostructures in electronic devices.

Precise simulation of the properties of electrons in nanostructures

Last year, two research teams succeeded independently of each other in fabricating narrow, atomically precise graphene nanoribbons and measuring their electron energies. The width of the nanoribbons varies in a precisely controlled manner. Each section of the nanoribbons has its own energy states with their own electronic structure. "However, the measurement results could not be completely reproduced by previous theoretical models," says Bonitz, who heads the Chair of Statistical Physics at ITAP. Together with his Ph.D. student Jan-Philip Joost and their Danish colleague Professor Antti-Pekka Jauho from the Technical University of Denmark (DTU), they developed an improved model which led to an excellent agreement with the experiments. The physicists present their theoretical results in the current issue of the renowned journal Nano Letters.

The basis for the new and more precise computer simulations was the assumption that the deviations between the experiment and previous models were caused by the details of the mutual repulsion of the electrons. Although this Coulomb interaction also exists in metals, and indeed was included in earlier simulations in a rough way, the effect is much greater in the small graphene nanoribbons, and requires a detailed analysis. The electrons are expelled from their original energy states and have to 'search' for other places, as Bonitz explains: "We were able to prove that correlation effects due to the Coulomb interaction of the electrons have a dramatic influence on the local energy spectrum".

The shape of nanoribbons determines their electronic properties

How the permissible energy values of the electrons depend on the length, width, and shape of the nanostructures has been clarified by the team by investigating many such nanoribbons. "The energy spectrum also changes when the geometry of the nanoribbons, their width, and shape, is modified," adds Joost. "For the first time, our new data allow precise predictions to be made as to how the energy spectrum can be controlled by specifically varying the shape of the nanoribbons," says Jauho from the DTU in Copenhagen. The researchers hope that these predictions will now also be tested experimentally and lead to the development of new nanostructures. Such systems can make important contributions to the further miniaturisation of electronics.
-end-
Original publication:

Jan-Philip Joost, Antti-Pekka Jauho, Michael Bonitz, Correlated Topological States in Graphene Nanoribbon Heterostructures, Nano Letters, (2019) DOI:10.1021/acs.nanolett.9b04075, https://pubs.acs.org/articlesonrequest/AOR-cxJ6Abf9gQsphD6q3TCH

Photos for download:

https://www.uni-kiel.de/de/pressemitteilungen/2019/375-Graphen.jpg

Caption: The graphene nanoribbon (center) consists of a single layer of honeycomb carbon atoms. The ribbon is only a few carbon atoms wide and has different electrical properties depending on its shape and width. The local density of the electrons is increased at the edges, as the dark red areas in the boxes show.

Copyright: Jan-Philip Joost, AG Bonitz

Scientific contact:

Prof. Dr. Michael Bonitz
Institut für Theoretische Physik und Astrophysik
Tel.: +49 431-880-4122
Mail: bonitz@theo-physik.uni-kiel.de
Web: http://www.theo-physik.uni-kiel.de/~bonitz

Details, which are only a millionth of a millimetre in size: this is what the priority research area "Kiel Nano, Surface and Interface Science - KiNSIS" at Kiel University has been working on. In the nano-cosmos, different laws prevail than in the macroscopic world - those of quantum physics. Through intensive, interdisciplinary cooperation between physics, chemistry, engineering and life sciences, the priority research area aims to understand the systems in this dimension and to implement the findings in an application-oriented manner. Molecular machines, innovative sensors, bionic materials, quantum computers, advanced therapies and much more could be the result. More information at http://www.kinsis.uni-kiel.de

Kiel University

Related Electrons Articles from Brightsurf:

Sticky electrons: When repulsion turns into attraction
Scientists in Vienna explain what happens at a strange 'border line' in materials science: Under certain conditions, materials change from well-known behaviour to different, partly unexplained phenomena.

Self-imaging of a molecule by its own electrons
Researchers at the Max Born Institute (MBI) have shown that high-resolution movies of molecular dynamics can be recorded using electrons ejected from the molecule by an intense laser field.

Electrons in the fast lane
Microscopic structures could further improve perovskite solar cells

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.

Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.

Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.

Using light to put a twist on electrons
Method with polarized light can create and measure nonsymmetrical states in a layered material.

What if we could teach photons to behave like electrons?
The researchers tricked photons - which are intrinsically non-magnetic - into behaving like charged electrons.

Read More: Electrons News and Electrons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.