Ultrafast optical pump-probe scanning tunneling microscopy

Since the invention of scanning tunneling microscopy (STM), the addition of high time-resolution to STM has been one of the most challenging issues, and various time-resolved STMs have been considered [1]. The most successful approach among them is to combine STM with electric and optical pump-probe (OPP) techniques [2-5]. In OPP-STM which we have been developing, the sample surface below STM tip is excited by a train of pulse pairs, similarly to the case of the OPP method, and tunneling current is measured as a function of delay time. In addition to the use of absorption bleaching mechanism, a new technique is to use THz pulses. Although it is difficult to apply a high bias voltage between the STM tip and sample in general, the tip-enhanced electric field obtained by ultrashort THz pulse enables it, and taking a snapshot of ultrafast dynamics becomes possible [6,7]. Control of the carrier envelope phases in pump and probe pulses paves the way for the development of new time-resolved analyses. Details will be discussed at the conference with recent results and the prospects for future researches.

[1] Terada, Y.; Yoshida, S.; Takeuchi, O.; and Shigekawa, H., J. Phys. Condens. Matter., 22, 264008-264015.
(2010) and references therein.
[2] Loth, S.; Etzkorn, M.; Lutz, C.P.; Eigler, D.M; and Heinrich, A.J., Science, 329, 1628-1630 (2010).
[3] Terada, Y.; Yoshida, S.; Takeuchi, O.; and Shigekawa, H., Nature Photonics, 4, 869-874 (2010).
[4] Cocker, T. L.; and Hegmann, F. A. et al., Nature Photonics, 7, 620-625 (2013).
[5] Yoshida, S.; and Shigekawa, H. et al., Nature Nanotechnology, 9, 588-593 (2014).
[6] Yoshioka, K.; Katayama, I.; Minami, Y.; Kitajima, M.; Yoshida, S.; Shigekawa, H.; and Takeda, J., Nature
, 10, 762-765 (2016).
[7] Cocker T.; Peller D.; Yu P.; Repp J.; and Huber R., Nature 539, 263-267 (2016).