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(1) Presentation(s)

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Jeu. 10/03/2022 10:00 Salle des Séminaires, Bâtiment 21, Etage 4

Séminaire
DIEZ Enrique (Group of Nanotechnology, USAL-NANOLAB, Universidad de Salamanca, Spain)
Exotic currents in nanodevices based on twisted angles in 2D materials

(Semi-conducteurs: Graphène, Grand gap & Photovoltaïque)


Sommaire:

Two-dimensional (2D) materials can be combined into complex heterostructures by stacking them with controlled twisted angles. Twisted layers of 2Ds present a modified band structure due to the presence of an induced Moiré pattern in their electronic structures. This field of research, commonly known as Twistronics, has blossomed recently due to the discovery of exotic states of matter in twisted bilayer graphene devices
However, this field of electronics offers many other lines of research, yet to be studied, with multiple applications and possible new effects. Our ongoing line of research focuses on the study of the appearance of exotic electronic states in heterostructures based on encapsulated graphene monolayer between two ultrathin layers of hexagonal boron nitride (hBN) by controlling the relative angle between the graphene and them.
In our latest devices, the three different layers are aligned with a commensurate pattern of the natural edges far away from the magic angle. Multiple alignment possibilities could happen following this procedure due to the two different crystalline directions of graphene and hBN, zigzag and armchair. By combining different optical and electrical measurements we can determine their exact relative alignment.
Low temperature electrical characterisation has determined, by local measurements, a high-quality sample with a sizeable mobility. The valley and spin degenerations are broken, and multiple plateaus appear when a magnetic field is applied. However, the most remarkable results of this device are not obtained with local measurements.
Magnetotransport measurements on this device have revealed an intriguing non-local electrical signal, with a chiral flavour, when small external magnetic fields are applied. The non-local signal in graphene is widely studied and different effects causing it can be found in the literature. However, very few effects can explain this chirality in the results.
There is no doubt that the study of different alignments among 2D materials opens many new possibilities in Twistronics, which could include a better understanding of anomalous superconductivity, paving the way for new methods to obtain materials with novel quantum properties. In addition to their undoubted fundamental interest, these materials may also enable new quantum technologies that constitute a technological breakthrough.


Pour plus d'informations, merci de contacter Nanot S.