Supplementary information
Hiroyuki Mogi1, Rin Wakabayashi1, Shoji Yoshida1, Yusuke Arashida1, Atsushi Taninaka1,2,Katsuya Iwaya 3, Takeshi Miura3, Osamu Takeuchi1, and Hidemi Shigekawa1*

1Faculty of pure and applied sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan

2 TAKANO Co. LTD. Miyada-mura, Kamiina-gun, Nagano, 399-4301 Japan

3 UNISOKU Co., Ltd., Hirakata, Osaka 573-0131, Japan

1 Faculty of pure and applied sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan

2UNISOKU Co., Ltd., Hirakata, Osaka 573-0131, Japan

E-mail: hidemi@ims.tsukuba.ac.jp

Supplementary note 1
In time-resolved STM, initially, absorption bleaching-type time-resolved STM, similar
to the optical pump-probe method, was realized1–3). Subsequently, the development of electricfield-driven time-resolved STM, which utilizes subcycle light with a controlled carrier envelope
phase (CEP) as an instantaneous bias voltage, was achieved4–10). In the absorption bleaching-typetime-resolved STM, by modulating the delay time or polarity of circularly polarized light, one
can perform stable measurements with a high signal-to-noise (S/N) ratio by eliminating the effectsof heat. This technique enabled the observation of phenomena in real space such as the impact ofsingle atomic-level defects on carrier dynamics and spin dynamics within individual quantum
wells11,12). Extensions to multiprobe STM are also advancing13–15). In electric-field-driven timeresolved STM, it is possible to evaluate the energy levels and densities of states of instantaneous
excitation states4–9). Initially, when using 1 ps THz pulse light, the time resolution wasapproximately 500 fs4,6–10,16). However, a time resolution of less than 30 fs has been achieved byemploying mid-infrared pulse light, enabling the analysis of band structure changes in nonequilibrium states5).

Supplementary note 2
For instance, in the case of p-type GaAs (doping concentration, 3.0 x 1017 cm-3;
depletion layer width, 45 nm), it has been revealed by time-resolved photoelectron spectroscopythat it takes a rise time of about 50 ps17). For the bulk WSe2 used in this study, considering thevery low mobility in the crystal c-axis direction (conductivity anisotropy, ~1200 18)) and thepossibility that the depletion layer width might be around ~120 nm19), it can be assumed that therise time of SPV is longer than the 45 ps laser pulse width used in this experiment.

Supplementary figure

Fig. S1 Results of measuring Δf responsive to the delay time modulation and the time variationof the phase on an oscilloscope (Vs = 0 V, Δf setpoint = +1 Hz, delay time modulation frequency= 20 Hz). Because we did not perform lock-in measurements, the effect of noise was pronounced.
To increase the S/N ratio, we increased the irradiation light intensity to approximately 7 mW toboost the signal strength and averaged 256 signal curves. First, it was confirmed that the phaselocked loop (PLL) feedback adequately tracks the frequency shift changes (PLL gain setup: PI
gain = 1.3 Hz/deg, PI integral cut off frequency = 80 Hz). As the delay time switching occurs
within one pulse cycle (2 μs), which is considerably faster than the PLL feedback bandwidth, anovershoot peak appears depending on the PLL feedback system's phase delay and gain settings.

This effect can be minimized by measuring only the in-phase component with a lock-in amplifier.
The attractive force was stronger when the delay was shorter, indicating that we captured the timeresolved signal through the image dipole force. Using a tuning fork and setting the measurement
conditions to the repulsive region with a small amplitude of 4 nm, the measurement of the nearfield forces by PiFM became straightforward.

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