Condensed Matter Theory Seminar - Jie Wang - “Exact fractional Chern insulators in flatbands with ideal quantum geometry”

Event time: 
Thursday, November 2, 2023 - 1:00pm to 2:00pm
Sloane Physics Laboratory SPL, Room 51 See map
217 Prospect Street
New Haven, CT 06511
Jie Wang - Harvard University
Event description: 

Moire material has been of intense interest for the range of correlated electron phenomena they exhibit and for their high degree of tenability. Recently, fractional Chern insulators (FCI) have been observed in various moire materials, including twisted TMD and graphene systems, opening promising future route towards experimental realization of non-abelian anyon and universal quantum computation. This talk presents an exact geometric criteria for the stability of FCI in general flatbands and discuss its implications. The common wisdom to find FCI is to engineer material to approach the limit with uniform Berry curvature. This talk will disprove such common lore by showing a new theory (ideal flatband) which emphasizes the fundamental importance of quantum metric. We prove ideal flatbands support exact zero energy ground state FCI for arbitrary amount of Berry curvature fluctuation for all nontrivial Chern number, and prove ideal quantum geometry alone can imply universal wavefunction and exactly closed density algebra. The ideal flatband is motivated by the chiral model of twisted bilayer graphene, but is a much general concept. It has direct implication for recently experimental observed FCI and composite Fermi liquid phases in moire materials.