Ultrafast nanoimaging of the order parameter in a structural phase transition

Understanding microscopic processes in materials and devices that can be switched by light requires experimental access to dynamics on nanometer length and femtosecond time scales. Here, we introduce ultrafast dark-field electron microscopy to map the order parameter across a structural phase transition. We use ultrashort laser pulses to locally excite a 1T-TaS2 (1T-polytype of tantalum disulfide) thin film and image the transient state of the specimen by ultrashort electron pulses. A tailored dark-field aperture array allows us to track the evolution of charge-density wave domains in the material with simultaneous femtosecond temporal and 5-nanometer spatial resolution, elucidating relaxation pathways and domain wall dynamics. The distinctive benefits of selective contrast enhancement will inspire future beam-shaping technology in ultrafast transmission electron microscopy.

Automated summary

This research introduces ultrafast dark-field electron microscopy to investigate the order parameter across a structural phase transition, using ultrashort laser pulses to locally excite a thin film and imaging the transient state of the specimen with ultrashort electron pulses. The study tracks the evolution of charge-density wave domains in the material with femtosecond temporal and 5-nanometer spatial resolution, revealing relaxation pathways and domain wall dynamics. The selective contrast enhancement in this study will inspire future advancements in beam-shaping technology for ultrafast transmission electron microscopy.