Extended Data Fig. 5: Voltage dependence of the photocurrent image in the transition range.

Photocurrent images over the FBPc molecule at −0.4, −0.3, −0.25, −0.2 and −0.1 V (Image size: 2.4 nm × 2.4 nm) acquired with the STM feedback loop open. The laser energy was set at the resonance of the S₀–S₁ transition, with a power of 77 μW. Shades of blue and red represent the current flow from the substrate to the tip and vice versa, respectively. The line profiles along the dashed line in each photocurrent image are shown below the respective images. The vertical dashed lines in the line profiles are for comparing the same tip positions. It is revealed that positions showing the local maximum of the positive photocurrent at −0.1 V correspond to where the negative photocurrent value shows a local minimum at −0.4 V. This result is indicative of the competition between the negative and positive photocurrent channels in the molecule.