New Approaches of Ultrafast Electron Microscopy for Quantum Materials

In this presentation, several of our research examples are selected to highlight the characterization of materials dynamics in strongly correlated systems. I will focus on ultrafast phenomena and charge-lattice and spin-lattice correlations. For instance, I will show: 1) a new two-color scheme based on near-field electron microscopy (PINEM), one for temporal gating, the other for pumping to achieve nm-fs spatiotemporal resolution to visualize ultrafast dielectric response and insulator-to-metal transition in nanowires [1]; 2) quantitative diffraction and diffuse scattering analysis to capture the photoinduced ultrafast atom dimerization and rotation dynamic pathways [2] and the evolution of optical and acoustic phonon population in charge-density-wave materials [3] using MeV-UED; and 3) study electromagnetic wave propagation in interdigitated comb device that is widely used as an antenna or sensor in mobile platforms [4] and observe spin wave dynamics under microwave excitation using the GHz electron pulser we developed at BNL. The ability to probe materials dynamic responses under RF excitations has promising applications for qubit devices and quantum information science. <br/> <br/>Work at BNL was supported by the DOE-BES-MSED under the grant DE-SC0012704.<br/> <br/>References:<br/>1. X. Fu, et al., "Nanoscale-femtosecond dielectric response of Mott insulators captured by two-color near-field UEM ", Nat. Comm., 11:5770 (2020).<br/>2. J. Li, et al., "Direct detection of V-V atom dimerization and rotation dynamic pathways upon ultrafast photoexcitation in VO2”, PRX 12, 021032 (2022). <br/>3. Y. Cheng et al., “Ultrafast formation of topological defects in a 2D charge density wave”, Nat. Phys., in press (2023) (arXiv:2211.05748).<br/>4. X. Fu, et al., "Laser-free ultrafast electron microscopy of electromagnetic wave dynamics", Sci. Adv., 6 eabc3456 (2020).