“Understanding Behavior of van der Waals Materials Using in-situ Transmission Electron Microscopy”
Thursday, Oct. 9 at 1 pm
MALA 5050
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Abstract
Development of new materials is essential to push the boundaries of our scientific understanding and is critical for meeting the growing demands for technology, and sustainability. Van der Waals (vdW) materials are one such candidate material platform that offer novel properties and functionalities which can enable breakthroughs especially in quantum sciences and microelectronics. It is essential to understand the behavior of the order parameter in these materials such as spin or lattice order, and the underlying energy landscape that governs such behavior. By gaining this understanding, we will be able to control and thus tailor their properties as desired. In this talk, we will present exploration of two different classes of van der Waals materials using in-situ transmission electron microscopy (TEM); (1) ferromagnetic vdW, and (2) charge density wave vdW.
Ferromagnetic vdW materials have been shown to exhibit several nontrivial magnetic spin structures, such as the Bloch or the Néel-type stripe domains, skyrmions, merons, or bubble domains. Lorentz transmission electron microscopy (LTEM) is ideally suited for quantitative analysis of magnetic domains and microstructure in such materials and related heterostructures. We will present results on ferromagnetic insulator: CrBr3 and ferromagnetic metal: Fe3GeTe2. Using in-situ cryo LTEM study of magnetic domains, we will elucidate the nature of the magnetic domains as well as the effect of local magnetic fields and electric currents on controlling the topology of the spin textures observed in these materials.
Strongly correlated vdW materials exhibit electron-electron and electron-lattice interactions which can lead to a rich landscape of ordered structural phases such as charge density waves (CDWs). Electrical stimulation of such CDW phases is extremely interesting since it can provide easy manipulation as well as leading to metal-insulator transitions. We will present results on the CDW phase in 1T-TaS2 using ultrafast electron microscopy. This unique capability that we have developed enables visualization of electrically triggered phenomena with the nanoscale spatial and nanosecond time resolution. We will show using time-resolved images the heterogeneous, mesoscopic strain dynamics in this material and discuss their implications for the electrical melting of CDWs for future memristive applications.
Biography
Charudatta Phatak, PhD, is the Deputy Division Director and the Group leader of the Nanoscale Magnetic and Electronic Heterostructures group in the Materials Science Division at Argonne National Laboratory. He is also an adjunct faculty in the Department of Materials Science and Engineering at Northwestern University. He received his Ph.D from Carnegie Mellon University in Materials Science and Engineering in 2009. His research interests are focused on exploring magnetic domain behavior and emergent topological excitations in magnetic nanostructures and 2D ferromagnets; understanding phenomena in oxides and quantum materials for low power, unconventional computing; development of advanced algorithms using machine-learning for phase retrieval and 3D tomographic reconstructions.