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Fractional Chern insulator states in an isolated flat band of zero Chern number

Datum
17.06.2025
Zeit
11:00 - 12:00
Sprecher
Dr. Zuzhang Lin
Zugehörigkeit
Department of Physics, The University of Hong Kong
Sprache
en
Hauptthema
Materialien
Host
Grit Rötzer
Beschreibung
A flat band with zero Chern number, and well isolated from the rest of Hilbert space by a gap much larger than interaction strength, is a context that has not been regarded as relevant for fractional quantum Hall physics. In this work, we present a numerical study to demonstrate the emergence of fractional Chern insulator (FCI) states in such isolated flat band with zero Chern number, which is hosted by a fluxed dice lattice with anisotropic hopping strength. While being topologically trivial, this flat band features an intriguing quantum geometry: the difference between the trace of quantum metric tensor and the Berry curvature is a constant. We consider nearest-neighbor repulsion that is weak enough to ensure that the isolated band limit is always satisfied, where band renormalization by interaction leaves the flat band quantum geometry unchanged and introduce a tiny band width only. At filling of the isolated flat band, our exact diagonalization calculations show unambiguous evidences for the FCI states, both from the many-body spectra and the many-body Chern number that demonstrates a fractionally quantized Hall conductance of e^2/3h. And the 3-fold ground state degeneracy on torus suggests that band-folding Hall crystal scenario is not compatible with the observed quantized Hall conductance at 2/3 filling. We find the finite dispersion acquired from interaction renormalization, albeit tiny in the isolated band limit, is necessary for FCI to emerge. With anisotropy getting stronger towards the disconnected-chains limit, the FCI undergoes a topological phase transition to inter-chain charge density wave. .
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Letztmalig verändert: 17.06.2025, 07:36:14

Veranstaltungsort

Leibniz Institut für Festkörper- und Werkstoffforschung Dresden (Zoom: , https://zoom.us/my/meeting.with.jeroen)Helmholtzstraße2001069Dresden
Homepage
http://www.ifw-dresden.de

Veranstalter

Leibniz Institut für Festkörper- und Werkstoffforschung DresdenHelmholtzstraße2001069Dresden
Homepage
http://www.ifw-dresden.de
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