Detecting ultrafast dynamics in correlated materials by laser-based photoelectrons
In strongly correlated systems, electron, spin, and phonon degrees of freedom are intricately intertwined, and various symmetry breaking phenomena occurs. These systems exhibit condensed states reflecting the interactions, thereby acquiring peculiar anisotropy and/or hierarchical structures which show unique dynamics in non-equilibrium states. Recently we have been working on observations of these dynamics by using new measurement techniques such as time- & angle-resolved photoelectron spectroscopy and ultrafast electron microscopy. In this talk, I will introduce our recent works on nematic iron-based superconductor FeSe and trimer-ordered “charge-density-wave” material VTe2. In FeSe, through the time-, energy-, momentum- and orbital-resolved photoelectron spectroscopy, we detected the ultrafast dynamics of the Fermi surface anisotropy, and found the short-lived nematic oscillation appearing right after the strong perturbation by light . In VTe2, we first clarified the electronic structure and found that the trimer formation is intimately related with the band inversion and the Dirac surface state located at the Brillouin zone boundaries . In addition, by using the ultrafast electron diffraction and imaging, we found the peculiar phononic responses related to the trimer dissolution by optical irradiation , suggesting the possibility of ultrafast control of band inversion. T. Shimojima, KI et al., Nat. Commun. 10, 1946/1-6 (2019).
 N. Mitsuishi, KI et al., Nat. Commun. 11, 2466/1-9 (2020).
 A. Nakamura, KI et al., Nano Lett. 20, 7, 4932–4938 (2020).
 T. Shimojima, KI et al, Sci. Adv. 7, eabg1322/1-8 (2021).
Chair: Masaki Oshikawa
This event is jointly organized by the Korea Institute for Advanced Study and the University of Tokyo. “Correlated Electrons Virtual International Seminars (CEVIS)” https://sites.google.com/view/cevis2020/home