Layer Hall counterflow as a model probe of magic-angle twisted bilayer graphene
Physical Review B(2023)
摘要
The recent constructions of flat moiré minibands in specifically twisted
multilayer graphene and twisted transition metal dichalcogenides (TMDs) have
facilitated the observation of strong correlations with a convenient
tunability. These correlations in flat bands result in the band dispersion
heavily influenced by carrier densities, leading to filling-dependent
quasiparticle band renormalizations. Particularly, in magic-angle twisted
bilayer graphene (MATBG), the band structure–including the quasiparticle
energy and wavefunction–is crucial in understanding the correlated properties.
Previous theoretical studies have demonstrated the presence of a
time-reversal-even charge Hall counterflow in response to a direct current (DC)
electric field in twisted bilayers as chiral structures. In this study, we show
that such layer Hall counterflow can serve as a sensitive probe for MATBG model
parameters, which are currently ambiguous as a result of unavoidable structural
relaxation and twist-angle disorder. We present the layer Hall counterflow and
the associated in-plane magnetization for three different MATBG continuum
models, based on which many-body interacting models have been widely applied to
study strong correlations in MATBG. At the single-particle level, our findings
indicate notable differences in layer-projected Hall conductivity, both in
magnitude and sign, between different MATBG continuum models. Furthermore, our
self-consistent Hartree calculations, performed on each of these
single-particle continuum models, reveal renormalized layer-projected Hall
conductivity by the self-consistent Hartree field.
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