QM Seminar Speaker Ahmed Abouelkomsan (Stockholm University), Wednesday, July 27 at 2:00 pm Pacific Time

Time/Venue Wednesday, July 27 at 2:00 pm Pacific Timein Physics South 402 and via Zoom:
https://berkeley.zoom.us/j/99523499113pwd=REovb3pyam03WXQwbEhrU3dqNHZvdz09

Meeting ID: 995 2349 9113 Passcode: 600704
Host Shubhayu Chatterjee/Joel Moore
Title Moiré Superlattices at Fractional Band Fillings:  Fractional Chern Insulators, Particle-Hole duality, and Quantum Geometry
Abstract We consider the core problem of Coulomb interactions within fractionally filled Moiré flat bands and demonstrate that the dual description in terms of holes, which acquires a non-trivial hole-dispersion, provides key physical intuition and enables more understanding for this strongly correlated problem. We find that the single-hole dispersion has a profound impact on the phase diagram in experimentally relevant examples such as ABC stacked trilayer and twisted bilayer graphene aligned with boron nitride. Such non-trivial particle-hole asymmetry which is generally absent in continuum Landau levels stems from the non-trivial underlying quantum geometry of the Moiré bands. In addition, we predict both twisted bilayer graphene aligned with boron nitride and gate-tunable twisted double bilayer graphene to be versatile platforms for the realization of fractional Chern insulator states like spin-singlet Halperin states and spin-polarized states in bands with Chern number C =1 and C = 2 at zero external magnetic fields.”

[1] Phys. Rev. Lett. 124, 106803 (2020)
[2] Phys. Rev. Lett. 126, 026801 (2021)
[3] arXiv:2202.10467

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