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
(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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