In April 2018, a group at MIT, USA, showed that it is possible to generate a form of superconductivity in a system of two layers of graphene under very specific conditions: To do this, the two hexagonal nets must be twisted against each other by exactly the magic angle of 1.1°. Under this condition a flat band forms in the electronic structure. The preparation of samples from two layers of graphene with such an exactly adjusted twist is complex, and not suitable for mass production. Nevertheless, the study has attracted a lot of attention among experts.
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But there is one more, much simpler way of flat band formation. This was shown by a group at the HZB (Helmholtz-Zentrum Berlin) around Prof. Oliver Rader and Dr. Andrei Varykhalov with investigations at BESSY II.The samples were provided by Prof. Thomas Seyller, TU Chemnitz. There they are produced using a process that is also suitable for the production of larger areas and in large quantities: A silicon carbide crystal is heated until silicon atoms evaporate from the surface, leaving first a single-layer of graphene on the surface, and then a second layer of graphene. The two graphene layers are not twisted against each other, but lie exactly on top of each other.
The premise is that a simpler method to achieve the proper structure can enable mass production.
Journal Reference:
D. Marchenko, D. V. Evtushinsky, E. Golias, A. Varykhalov, Th. Seyller, O. Rader. Extremely flat band in bilayer graphene. Science Advances, 2018; 4 (11): eaau0059 DOI: 10.1126/sciadv.aau0059
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The discovery is a significant advance in an emerging field called Twistronics, whose pioneers include MacDonald and engineer Emanuel Tutuc, also from The University of Texas at Austin. It took several years of hard work by researchers around the world to turn MacDonald's original insight into materials with these strange properties, but it was worth the wait.
See also: A Physics Magic Trick: Take 2 Sheets of Carbon and Twist
Previously: Graphene on the Way to Superconductivity
Graphene (With a Twist) Is Helping Scientists Understand Superconductors
(Score: 2) by RandomFactor on Saturday November 10 2018, @02:36PM
Link to the article in English - https://www.helmholtz-berlin.de/index_en.html [helmholtz-berlin.de]
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(Score: 4, Interesting) by RandomFactor on Saturday November 10 2018, @02:57PM
The linked article doesn't indicate what temperature this would occur at that I saw. There is a reference to this on wikipedia already that does make a mention of temperature
A new superconductor is less interesting if we still have to immerse it in liquid nitrogen, but even removing all the fancy doping of atoms for higher temperature superconductors would be nice in and of itself.
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