Multi-photon photoexcitation of transition metal dichalcogenides: recent development

Cheng-Tien Chiang^1,2,3,4*, Mukesh Singh¹, Prabesh Bista^1,2,5, Yu-Chan Lin¹, Chia-Nung Kuo⁶, Chin Shan Lue^6,7

¹Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
²Molecular Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan
³Department of Physics, National Taiwan University, Taipei, Taiwan
⁴Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
⁵Department of Physics, National Central University, Taoyuan, Taiwan
⁶Department of Physics, National Cheng Kung University, Tainan, Taiwan
⁷Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taiwan

* Presenter:Cheng-Tien Chiang, email:ctchiang@pub.iams.sinica.edu.tw

With the recent progress of intense ultrafast laser technology, multi-photon absorption in solids has become possible [1]. In a multi-photon transition, not only the occupied electronic states below the Fermi energy participate, but also the unoccupied electronic states can play an important role [2]. These originally unoccupied states are transiently populated via the nonlinear optical transitions, and their interaction with the surrounding electronic states as well as collective excitations such as phonons and magnons can lead to their decay on the femtosecond to picosecond time scale [3]. In addition to the pure academic interest in studying these unoccupied electronic states via multi-photon transitions, their detailed properties could also have implications for the potential applications of opto-electronic devices [4].

In order to directly resolve the possible relevant unoccupied electronic states on the advanced two-dimensional materials transition metal dichalcogenides, time-resolved multi-photon photoelectron spectroscopy has been developed worldwide over the last decades [5]. In this invited talk, a short overview of the current status of these experiments will be given. Afterwards our recent progress of experimental development will be discussed in detail with two- and three-photon photoemission on NiTe₂ as examples.

[1] T. Brabec and F. Krausz, Rev. Mod. Phys. 72, 545 (2000).
[2] L. D. Laude and M. Wautelet, IL Nuovo Cimento 39, 734 (1977); F. Bisio et al., Phys. Rev. Lett. 96, 087601 (2006).
[3] P. M. Echenique et al., Surf. Sci. Rep. 52, 219 (2004).
[4] X.-Y. Zhu, J. Phys. Chem. Lett. 5, 2283 (2014); R. Haight, Surf. Sci. Rep. 21, 275 (1995).
[5] J. Liu et al., Phys. Chem. Chem. Phys. 23, 26336 (2021); A. Tanaka et al., Phys. Rev. B 67, 113315 (2003).

Keywords: 2D material, transition metal dichalcogenide, photoemission, ultrafast optics, electron dynamics