Unveiling Phase Transitions in 2D Layered Materials via Atomic-Scale Cryogenic STEM

Quantum materials exhibit unique phenomena and functionalities beyond classical physics. The use of 2D sheets, heterogeneous interfaces, and moiré structures has emerged as a promising method to induce exotic quantum effects. However, studying these materials using cryogenic scanning transmission electron microscopy (STEM) has been limited by stage instability. Achieving stable atomic-scale imaging at cryogenic temperatures, particularly in techniques like atomic-scale 4D-STEM imaging and monochromated electron energy loss spectroscopy (EELS), is expected to provide valuable information for probing key parameters in quantum materials. Recent improvements in stage designs and machine learning-assisted acquisition and analysis algorithms offer opportunities for related research. In this presentation, I'll discuss our on-going research using cryogenic STEM and EELS to study lattice-spin-charge coupling in 2D van der Waals materials for spintronics applications, with a specific focus on our findings regarding layer-dependent atomic structural transitions and magnetic behavior alterations for spintronics applications. Additionally, we'll cover local temperature calibration methods for cryogenic STEM and the application of machine learning for data acquisition and analysis in achieving multi-dimensional STEM mappings at cryogenic temperatures, including atomic-resolution 4D-STEM imaging and spectroscopy.