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Résumé |
Progress in stacking two dimensional materials, such as graphene or transition metal dichalcogenides
(TMDs), has paved the way to engineer new structures relying on moire patterns. These patterns induced for
example by slightly twisting one layer compared to the other, could lead to strongly correlated quantum
phases such as superconductivity or the quantum anomalous Hall effects. In the realm of condensed matter
physics, the fractional quantum Hall effect stands as a singular experimental manifestation of topological
order, characterized by the presence of anyons—quasiparticles that bear fractional charge and exhibit
exchange statistics diverging from conventional fermions and bosons. This phenomenon, observed over four
decades ago, was still missing the direct observation of similar topological orders arising purely from band
structure—without the application of strong magnetic fields. In 2023 within the span of a few months, several
pioneering experiments have illuminated this once theoretical domain. Studies on twisted homobilayer MoTe2
and pentalayer rhombohedral graphene placed on hBN have finally unveiled the existence of fractional Chern
insulators (FCIs), the zero-magnetic field analog of fractional quantum Hall states.
The journey to this point, preceded by over a decade of theoretical frameworks and predictions surrounding
FCIs, yet the experimental revelations have proved to be richer and more surprising than expected. In this
talk, we will present how the combination of ab-initio and quantum many-body calculations can help us
capture the different features observed in experiments. We will discuss the potential future for this exciting
booming field, including the possible observation of fractional topological insulators, a yet-never observed
topological ordered phase preserving the time reversal symmetry. |
