Link between cascade transitions and correlated Chern insulators in magic-angle twisted bilayer graphene
arxiv(2024)
Abstract
Chern insulators are topologically non-trivial states of matter characterized
by incompressible bulk and chiral edge states. Incorporating topological Chern
bands with strong electronic correlations provides a versatile playground for
studying emergent quantum phenomena. In this study, we resolve the correlated
Chern insulators (CCIs) in magic-angle twisted bilayer graphene (MATBG) through
Rydberg exciton sensing spectroscopy, and unveil their direct link with the
zero-field cascade features in the electronic compressibility. The
compressibility minima in the cascade are found to deviate substantially from
nearby integer fillings (by Δν) and coincide with the onsets of CCIs
in doping densities, yielding a quasi-universal relation
B_c=Φ_0Δν/C (onset magnetic field B_c, magnetic flux quantum
Φ_0 and Chern number C). We suggest these onsets lie on the intersection
where the integer filling of localized "f-orbitals" and Chern bands are
simultaneously reached. Our findings update the field-dependent phase diagram
of MATBG and directly support the topological heavy fermion model.
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