This study uses ultrafast electron microscopy (UEM) to visualize the ultrafast evolution of a three-dimensional (3D) photoemitted electron gas in a static magnetic field. A 3D hot electron gas is created via two-photon photoemission from a copper surface. The subsequent electron dynamics are characterized by a shape transformation from oblate to prolate, and by periodic cyclotron oscillations. These oscillations create a transient lensing effect, distorting the images. An analytical expression for the time-dependent focal length is derived, and simulations explore the roles of Coulomb self-fields and image charges. This work opens avenues for visualizing cyclotron dynamics in 2D electron gases and advancing understanding of electron/plasma dynamics.

Omid Zandi, Allan E. Sykes, Ryan D. Cornelius, Francis M. Alcorn, Brandon S. Zerbe, Phillip M. Duxbury, Bryan W. Reed, Renske M. van der Veen