Berlin 2024 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 8: Ultrafast Phenomena I

HL 8.10: Vortrag

Montag, 18. März 2024, 17:30–17:45, EW 015

Ultrafast Nanobeam Electron Diffraction of Charge-Density Wave Phase Transitions at Megahertz Rates — •Till Domröse^1,2 and Claus Ropers^1,2 — ¹Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany — ²4th Physical Institute, University of Göttingen, Germany

Ultrafast electron diffraction (UED) is capable of unveiling ultrafast structural dynamics in functional materials [1]. Its intrinsic spatial averaging, however, limits the characterization of nanoscale heterogeneity, which often decisively influences the dynamics, or even is a source of functionality itself. Here, we demonstrate how the high-coherence electron source of the Göttingen Ultrafast Transmission Electron Microscope (UTEM) [2] enables the formation of highly collimated, nanometer-sized, femtosecond electron pulses for UED. We investigate laser-induced charge-density wave dynamics in the strongly-correlated materials 1T-TaS₂ and 1T-TaTe₂ at an unprecedented repetition rate of up to 2 MHz. Therein, the high reciprocal-space resolution allows us to identify a light-induced hexatic state via a three-dimensional characterization of transient disorder [3]. Furthermore, the significant signal enhancement in combination with the small probe volume facilitates access to laser-induced phase transitions with high sensitivity, paving the way for the investigation of non-equilibrium structural dynamics in heterogeneous systems on their intrinsic timescales.

[1] D. Filippetto et al., Rev. Mod. Phys. 94, 045004 (2022)

[2] A. Feist et al., Ultramicroscopy 176, 63-73 (2017)

[3] T. Domröse et al., Nat. Mater. 22, 1345-1351 (2023)

Keywords: Ultrafast electron diffraction; Structural phase transitions; Charge-density waves; Ultrafast Transmission Electron Microscopy; Strongly-correlated materials