Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Yaniv Kurman (1) , Raphael Dahan (1) , Hanan Herzig Sheinfux (2) , Kangpeng Wang (1) , Michael Yannai (1) , Yuval Adiv (1) , Ori Reinhardt (1) , Luiz Tizei (3) , Steffi Woo (3) , Jiahan Li (4) , James Edgar (4) , Mathieu Kociak (3) , Frank Koppens (2, 5) , Ido Kaminer (1)

1 Technion - Israel Institute of Technology [Haifa]
2 ICFO - Institut de Ciencies Fotoniques [Castelldefels]
3 LPS - Laboratoire de Physique des Solides
4 Kansas State University
5 ICREA - Institució Catalana de Recerca i Estudis Avançats = Catalan Institution for Research and Advanced Studies

Coherent optical excitations in two-dimensional (2D) materials, 2D polaritons, can generate a plethora of optical phenomena that arise from the extraordinary dispersion relations that do not exist in regular materials. Probing of the dynamical phenomena of 2D polaritons requires simultaneous spatial and temporal imaging capabilities and could reveal unknown coherent optical phenomena in 2D materials. Here, we present a spatiotemporal measurement of 2D wave packet dynamics, from its formation to its decay, using an ultrafast transmission electron microscope driven by femtosecond midinfrared pulses. The ability to coherently excite phonon-polariton wave packets and probe their evolution in a nondestructive manner reveals intriguing dispersion-dependent dynamics that includes splitting of multibranch wave packets and, unexpectedly, wave packet deceleration and acceleration. Having access to the full spatiotemporal dynamics of 2D wave packets can be used to illuminate puzzles in topological polaritons and discover exotic nonlinear optical phenomena in 2D materials.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Yaniv Kurman, Raphael Dahan, Hanan Herzig Sheinfux, Kangpeng Wang, Michael Yannai, et al.. Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons. Science, 2021, 372 (6547), pp.1181-1186. ⟨10.1126/science.abg9015⟩. ⟨hal-03325434⟩