« All Events
Materials Science Seminar Series presents Professor Judy Cha on Thursday, November 2, from 4 to 5 p.m. The seminar is hosted by Professor Dan Rhodes and will be held in MS&E building room 265. Prof. Judy Cha will be discussing in situ cryo 4D STEM of CDW phase transitions in layered materials.
Many quantum materials possess complex electronic phase diagrams where correlated electronic phases, such as superconductivity, magnetic ordering, and charge density waves (CDWs), exist near each other. The proximity of these phases suggests that phase transitions must be understood to establish the microscopic origin for these correlated phases and to use them for applications. These phase transitions have mostly been studied using ensemble-measurement techniques, lacking real space information of nucleation and growth of these often-competing electronic phases. Nevertheless, such real-space information is essential for applications of quantum materials, which will be at the nanoscale where reduced dimensionality, confinement, local heterogeneities, interfaces, and defects will greatly modify the phase transitions.
In this talk, I will discuss our group’s efforts on combining cryogenic scanning transmission electron microscopy (STEM) and in situ cryo 4D STEM with in situ transport measurements to study the phase transition of TaS2 in real-space with nanometer resolution as it undergoes a transition from the commensurate CDW (insulating phase) to the nearly commensurate CDW (metallic phase). We directly visualize the nucleation and growth of the NC-CDW phase out of the C-CDW phase and correlate this to the changing transport data. We establish that the phase transition starts at extended defects present in TaS2. Our findings are extended to CDWs in rare-earth tri-tellurides (RTe3) and other layered materials.
Judy J. Cha is a professor in the Department of Materials Science and Engineering at Cornell University. She received her Ph.D. in Applied Physics from Cornell University in 2009 and did her post-doc research at Stanford University in the Department of Materials Science and Engineering. Before joining Cornell in 2022, she was a faculty member in the Dept. of Mechanical Engineering and Materials Science at Yale University. She is a recipient of the SRC Young Faculty Award (2021), the Gordon & Betty Moore EPiQS Synthesis Investigator Award (2019), the NSF CAREER (2018), the Canadian Institute for Advanced Research (CIFAR) Azrieli Global Scholar for quantum materials (2017), the Yale Arthur Greer Memorial Prize (2016), and the IBM Faculty Award (2014).