Fig. 1. Energy level diagram of tunneling junction. Applied bias shifts Fermi level by e_V

Fig. 2. Optical setup for THz-STM based on large-area photoconductive antenna^[38]

Fig. 3. Optical setup for THz-STM based on optical rectification in lithium niobate crystal^[60]

Fig. 4. THz-STM scanning results on silicon surface^[38]. (a) STM images obtained using optical pump-terahertz probe with constant-height tip, in which image size is 13 nm×13 nm; (b) relative height curve obtained by horizontal line scan; (c) unit cell for Si(111)‑(7×7) surface reconstruction

Fig. 5. THz-STS of atomically precise graphene nanoribbons^[43]. (a) Tip positions for THz-STS overlaid on diagram of physical structure of 7-AGNR (left) and terahertz-induced charge distribution map (right), where diamonds denote anti-node position and circles represent node position; (b) differential conductance curves extracted from fitting curves of measured data at anti-node position (left) and node position (right), respectively; (c) lightwave-driven scanning tunneling tomography, acquired at ETHz,pk=-180V/cm (left) and ETHz,pk=+180V/cm (right)

Fig. 6. Ultrafast tracking of pentacene molecular motion^[10]. (a) Schematic of pump-probe experiment; (b) measurement of single pentacene molecule’s dynamics in pump-probe experiment, where tunneling current due to the second pulse shows obvious coherent oscillations

Fig. 7. Sub-cycle atomic-scale forces coherently control single-molecule switch^[39]. (a) Schematic of pump-probe experiment; (b) mean p¯ (left) and amplitude ppp (right) of switching probability curves as functions of equivalent voltage VTHzpump generated by pumping terahertz pulses