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Link between structural and electronic properties of moirés of graphene studied by scanning tunneling microscopy

Mercredi 29 novembre 2017 14:00 - Duree : 2 heures
Lieu : Salle de réunion du bâtiment accueil (A2), CEA, 17 rue des Martyrs

Orateur : Soutenance de Thèse de Loïc HUDER (INAC/PHELIQS)

The superimposition of two mismatched periodic patterns leads to the apparition of a moiré pattern. In condens ed-matter physics, the moiré pattern is known to occur in Scanning Tunneling Microscopy (STM) images of two superimposed atomic layers with a twist angle and/or a lattice parameter difference between the two lattices. The moiré pattern depends highly on these mismatches and in addition acts as a superperiodic potential on the electrons. This leads to a strong link between the structure and the electronic properties of moiré systems. In this thesis, this link was studied in twisted graphene layers, i.e. the misorientated stacking of two graphene layers, using STM at low temperatures. Detailed analyses of STM images show that not only rotation but also strain between the layers are involved in the formation of the moiré pattern. Even rather small relative strain has a distinct signature on the measured electronic density of states that is well reproduced by theoretical calculations. This link was also exploited by inducing deformations in the graphene layer with the STM tip to trigger changes in the local electronic density of states of the moiré system. Finally, the growth of graphene on high-quality tantalum carbide was studied revealing the formation of moirés of graphene in which superconductivity was induced by proximity effect.

Contact : loic.huder@cea.fr

Discipline évènement : (Physique)
Entité organisatrice : (INAC/SPSMS)
Nature évènement : (Soutenance de thèse)
Site de l'évènement : Site CEA sans badge requis

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