Generation and control of non-local chiral currents in graphene superlattices by orbital Hall effect*

In this study, we present electrical measurements on single-layer graphene Hall-bars that are encapsulated within hexagonal boron nitride thin films and have a controlled twisting angle between the layers. The samples were fabricated using a cryo-etching method, which allowed us to achieve unprecedented control over the roughness of the edges. The entire structure was placed onto a thin graphite back gate to prevent dopants or trapped charges that can arise from standard semiconductor substrates.

 

We conducted a comprehensive study of the magnetotransport reponse of the structure at different temperatures, applying an in to-out-of-plane external field and paying special attention to the possible effects arising due to the Moiré pattern.

 

We present local and non-local signals and report a striking chiral behavior of the nonlocal currents at low magnetic fields resulting from a charge carrier-valley coupling. This behavior is in stark contrast to previous results of similar structures at different twisting angles. The presented chiral response is found to be caused by the orbital valley Hall effect, with thorough theoretical calculations supporting our experimental results.