Electric field tunable bands in a doubly aligned bilayer graphene hBN moiré superlattice

In this paper, we demonstrate electric-field-induced band modification of an asymmetrically twisted doubly aligned bilayer graphene hBN (hBN/BLG/hBN) supermoir\'e lattice. Distinct from unaligned BLG/hBN systems, we observe regions in the density-displacement field $(n\text{\ensuremath{-}}D)$ plane where the device conductance is independent of $n$ and decreases as $|D|$ increases. This distinction arises due to the angle asymmetry between the layers, which induces field-controlled layer polarization. We identify $D$-dependent additional band gaps near the charge neutrality point that appear in the conduction (valence) band for negative (positive) $D$ values. In the quantum Hall regime, different sixfold degenerate Landau levels are observed. Our findings establish that in an asymmetric supermoir\'e heterostructure, an external vertical displacement field affects the valence and conduction bands very differently and sheds light on the asymmetric conductance patterns noted in previous studies.