Unexpected quantum effects in natural double-layered graphene

Graphene on a piece of tape. Credit: Christoph Hohmann (MCQST Cluster)

An international research team led by the University of Göttingen has detected new quantum effects in high-precision studies of natural double-layered graphene and interpreted them with the University of Texas at Dallas using their work theoretical. This research brings new knowledge on the interaction of charge carriers and the different phases, and contributes to the understanding of the processes involved. The LMU in Munich and the National Institute of Materials Science in Tsukuba, Japan also participated in the research. The results were published in Nature.

The new material graphene, a thin layer of carbon atoms, was first discovered by a British research team in 2004. Among other unusual properties, graphene is known for its extraordinarily high electrical conductivity. If two individual layers of graphene are twisted at a very specific angle to each other, the system even becomes superconductive (i.e. conducts electricity without any resistance) and exhibits other effects exciting quantums such as magnetism. However, the production of such twisted graphene double layers has so far required increased technical efforts.

This new study used the natural double-layered form of graphene, where no complex fabrication is required. First, the sample is isolated from a piece of graphite in the laboratory using a simple adhesive tape. To observe the effects of quantum mechanics, the Göttingen team then applied a high electric field perpendicular to the sample: the electronic structure of the system changes and a strong accumulation of charge carriers of similar energy occurs.

At temperatures just above absolute zero of minus 273.15 degrees Celsius, graphene’s electrons can interact with each other and a variety of complex quantum phases emerge in completely unexpected ways. For example, the interactions cause the spins of the electrons to align, making the material magnetic without further outside influence. By altering the electric field, researchers can permanently change the strength of charge carrier interactions in double-layered graphene. Under specific conditions, electrons can be so restricted in their freedom of movement that they form their own electron network and can no longer contribute to charge transport due to their mutual repulsive interaction. The system is then electrically insulating.

“Future research can now focus on studying other quantum states,” says Professor Thomas Weitz and Ph.D. student Anna Seiler, Faculty of Physics, University of Göttingen. “In order to access other applications, for example new computing systems such as quantum computers, researchers should find how these results could be obtained at higher temperatures. However, a major advantage of the current system developed in our new research lies in the simplicity of manufacturing the materials.”

New quantum effect discovered in natural graphene

More information:
Anna M. Seiler et al, Quantum Cascade of Correlated Phases in Trigonally Deformed Bilayer Graphene, Nature (2022). DOI: 10.1038/s41586-022-04937-1

Provided by the University of Göttingen

Quote: Unexpected Quantum Effects in Natural Double-Layer Graphene (August 15, 2022) Retrieved August 15, 2022 from https://phys.org/news/2022-08-unexpected-quantum-effects-natural-double-layer.html

This document is subject to copyright. Except for fair use for purposes of private study or research, no part may be reproduced without written permission. The content is provided for information only.

Leave a Reply