Twisted graphene moiré superlattice has been demonstrated as an exotic platform for investigating correlated states and nontrivial topology. Among the moiré family, twisted double bilayer graphene (TDBG) is a tunable flat band system expected to show stacking-dependent topological properties. However, electron correlations and the band topology are usually intertwined in the flat band limit, rendering the unique topological property due to stacking still elusive. Focusing on a large-angle TDBG with weak electron correlations, we probe the Landau level (LL) spectra in two differently stacked TDBG, i.e., ABBA- and ABAB-TDBG, to unveil their distinct topological properties. For ABBA-TDBG, we observe nontrivial topology at zero electric field $D=0$, evident from both the emergence of Chern bands from half-fillings $v=\pm 2$ and a giant orbital magnetic momentum. For ABAB-TDBG, by contrast, we find that the moiré band is topologically trivial at $D=0$, supported by the absence of LLs from half-fillings and the persistence of the gap at CNP above the critical magnetic fields. In addition, we also observe an evolution of the trivial-to-nontrivial topological transition at $D\ne 0$, confirmed by the emerged Landau fans originating from quarter-filling $v=1$. Our result demonstrates, for the first time, the unique stacking-dependent topology in TDBG, offering a promising avenue for future investigations on topological states, as well as correlated states, in dispersive band limits.

Close

PrevNext

View figure in article

• Landau levels
• Symmetry protected topological states
• Transport phenomena
• Twistronics
• Graphene