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TITLE: [GS_C_MS] Visualizing Emerging Orders in Matter with Electron Microscopes

ABSTRACT: Recent advances in electron microscopy now allow us to directly visualize complex structural phenomena and exotic orderings in materials at the single-atom level. In this talk, I will introduce a complementary momentum-resolved technique, 4D-STEM, performed under cryogenic conditions using a liquid helium holder. This approach enables spatial mapping of charge density wave (CDW) correlations across the phase transition in 2H-NbSe2. I will discuss how the evolution of CDW correlation length reveals critical-like behavior near the transition temperature, opening new pathways for probing phase transitions in low-dimensional quantum materials. If time permits, I will also introduce the fundamental principles of atomic electron tomography (AET), a technique capable of determining the full 3D atomic structure of individual nanomaterials without crystallographic averaging. I will present our recent work on visualizing three-dimensional topological polar ordering in ferroelectric nanoparticles, providing direct atomic-scale evidence of exotic polar textures relevant to topology and functional control in oxides—purely originating from surface boundary conditions, without the need for epitaxial strain.