Imaging nanoscale photocurrent in the twisted bilayer graphene by magneto-scanning near-field optical microscopy

In graphene, one main mechanism for generating photocurrent is the thermoelectric effect. For the twisted bilayer graphene (TBG), photocurrent induced by optical thermoelectric effect has been used to probe the local superlattice structure and electronic structure in nanoscales^1,2, while the effect of high magnetic field on nano-photocurrent has never been explored. Here in this talk, using the newly developed magneto-scanning near field optical microscopy (m-SNOM), we will show nano-photocurrent measurements in TBG samples under high magnetic field up to 7T and discuss these magneto-photocurrent phenomena in terms of thermal Nernst effect.

1. Sai S. Sunku, et al., Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene, Nano Lett. 20, 2958 (2020).

2. Niels C. H. Hesp, et al., Nano-imaging photoresponse in a moiré unit cell of minimally twisted bilayer graphene, Nature Commun. 12, 1640 (2021).