Simulation on tip-induced nanoscale magneto-photocurrent in 2-dimensional electron systems

Lattice symmetry and electron properties of 2-dimensional (2D) materials can be investigated by measuring photocurrent. In this work, we use the magneto scanning near-field optical microscope (m-SNOM) to map the nanoscale photocurrent of graphene under a magnetic field. Via tip-enhanced optical excitation and tip-induced local thermogradient, the magnetic field yields an anisotropic magnetothermal effect. We will show our simulation of the 2D nanoimaging of tip-initiated photocurrent/voltage with varying temperatures, magnetic field, incident photon energy, and electric properties of 2D electron systems. We found that our toy model matches recent experiments very well. The calculation predicts a quantized and edge photocurrent which would be observed by m-SNOM at low temperatures in future experiments.