Visualizing individual atoms, particularly light elements like oxygen and hydrogen, has long been a challenge in electron microscopy due to issues like multiple scattering and beam damage. In this talk, I will introduce multislice electron ptychography (MEP), a breakthrough technique that enables the record-breaking-resolution reconstruction of 3D atomic structures with exceptional dose efficiency, even in relatively thick samples. I will begin by introducing MEP and its practical implementation. I will then present two groundbreaking applications that highlight MEP’s potential. First, we use MEP to map critical oxygen point defects–vacancies and interstitials–in Ruddlesden-Popper nickelate superconductors, uncovering a direct correlation between local oxygen ordering and the charge carrier density that governs superconductivity. Next, I will demonstrate how MEP enables visualization and quantification of hydrogen atoms in metal hydrides, offering new insights into hydrogen storage and its dynamics. Finally, I will discuss the perspective of MEP, focusing on its exciting potential for studying hidden orders and in situ dynamic processes in functional materials.
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