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Magic angle twisted bilayer graphene has emerged in the past decade as a platform for non-conventional superconductivity. This behavior arises in the presence of a localized flat band as the twist angle approaches a well-defined value referred to as the magic angle, shown in a pioneering theoretical work. This theoretical prediction was later confirmed by experiments, giving more details on the superconducting behavior of magic angle twisted bilayer graphene. Of particular interest is the observed symmetry breaking between hole and electron doping that is characteristic of this type of superconductivity.
This topology drives the Fermi level away from the charge neutrality point, causing partially filled flat bands in magic-angle . This deformation also causes a charge redistribution in the twisted bilayer, causing a particular broken symmetry (central inset in
Figure 1b) typically observed in high temperature superconductors and reported in magic-angle twisted bilayer graphene. The findings of the team also explain several exciting experimental observations in magic-angle, including striped charge order and evolution of the vibrational spectra, neither of which can be explained in terms of the conventional deformation mode with pure screw dislocations.
The understanding of moiré physics deriving from dislocation concepts makes it possible to rationalize these and many other observed features within a well-established framework. Additional findings may yet emerge from this dislocation model for the moiré structure in twisted bilayer graphene. Indeed, while solitons provide one simple framework for understanding moiré patterns, there is no comparable concept of helical solitons…but helical dislocations have been observed in materials for more than seven decades!
 Rakib T, Pochet P, Ertekin E and Johnson H TCorrugation-driven symmetry breaking in magic-angle twisted bilayer graphene.Communications Physics 2022
 Rakib T, Pochet P, Ertekin E and Johnson H THelical dislocation in twisted bilayer graphene.Extreme Mechanics Letters 2023
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