Imaging topological edge states in twisted bilayer graphene

Stacking two 2D materials layers with a slight twist misalignment generates an additional larger periodic structure known as moiré pattern. These moiré bilayers have been shown to exhibit highly interesting physical phenomena, such as unconventional superconductivity in magic angle twisted bilayer graphene (t-BLG) [1], and novel moiré localized excitons transition metal dichalcogenide heterostructures [2]. Recently, we demonstrated that t-BLG has non-trivial topology at the moiré superlattice (SL) band gaps and that it exhibits a unique strong non-local resistance when Fermi-level is within these SL gaps [3]. Herein, by measuring the low temperature magneto-transport properties in MoRe/t-BLG/MoRe Josephson junctions (JJs), we were able to reconstruct the real-space current distribution in t-BLG, which allowed us to decipher the edge and bulk contributions and elucidate the physical origin of the non-local response in t-BLG. These results lay the groundwork to understand and control topological edge states in moiré heterostructures and bilayers.

 

[1] Cao, Y. et al. Nature 2018, 556, (7699), 43.

[2] Yu, H. et al. Science Advances 2017, 3, (11), e1701696.

[3] Ma, C. et al. Nano Letters 2020, 20, (8), 6076-6083.