Transport and spectral properties of magic-angle twisted bilayer graphene junctions based on local orbital models

The electronic properties of junctions defined electrostatically on twisted bilayer graphene can be addressed theoretically using lattice models. Recent works have introduced minimal local orbital models to describe twisted bilayer graphene at the magic angle (MATBLG) with different degrees of approximation and accounting for fragile topology. Based on these models and using Green's function techniques we analyze in this work the spectral and transport properties for MATBLG defined along different types of edges. To this end we first study the effect of symmetry breaking perturbations on the bulk bands, identifying their topological character. In a second step we obtain results for the local spectral densities at open boundaries and for two terminal transport on a three region junction where one could control independently the central and lateral regions doping level. Due to the large moire length we observe that the hybridization of chiral edge states on these junctions gives rise to a signature in the longitudinal transport and to asymmetries in the local densities of states. We further show that these properties are extremely sensitive to the orientation of the junctions along the moire lattice.

Automated summary

This study theoretically addresses the electronic properties of junctions defined electrostatically on twisted bilayer graphene using lattice models and Green's function techniques. The analysis reveals the impact of symmetry breaking perturbations on bulk bands and the sensitivity of structural orientation on the resulting features in spectral and transport properties. The hybridization of chiral edge states on these junctions leads to distinct signatures in longitudinal transport and local densities of states.