Coulomb drag in graphene/hBN/graphene moiré heterostructures

Yueyang Wang, Hongxia Xue, Kenji Watanabe, Takashi Taniguchi, Dong-Keun Ki

Published 2024-05-30Version 1

We report on the observation of Coulomb drag between graphene-hexagonal boron nitride (hBN) moir\'e heterostructure with a moir\'e wavelength of ~10 nm and an intrinsic graphene with a lattice constant of ~0.25 nm. By tuning carrier densities of each graphene layer independently, we find that the charge carriers in moir\'e mini-bands, i.e., near the satellite Dirac point (sDP), can be coupled with the massless Fermions near the original Dirac point (oDP), strongly enough to generate a finite drag resistance. At high temperature ($T$) and large density ($n$), the drag resistances near both oDP and sDP follow a typical $n^{-1.5}$ and $T^2$ power law dependence as expected for the momentum transfer process and it also satisfies the layer reciprocity. In contrast, at low $T$, the layer reciprocity is broken in both regions that suggest dominant energy drag. Furthermore, quantitatively, the drag resistances near sDPs are smaller than those near oDP and they deviate from $T^2$ dependence below ~100 K. These results suggest that the coupling between the carriers in moir\'e mini-bands and those in original Dirac bands may not be of a simple Fermi liquid nature.