Physics Colloquium: Curious cases of electrons in fullerene materials under laser lights and particle impacts

Shining laser lights on an atom or colliding the atom with charged particles one can probe the atom’s response to such external stimuli. These are powerful methods to access fundamental properties of materials. Using these techniques to nanosystems, far more complex than atoms and of direct applied interests, is beneficial for advancements of basic science and technology. The systems of our current interests are Buckminster fullerenes and larger fullerenes, including atoms/clusters caged inside them, called the endofullerenes. These materials hold the promise of applications in areas of quantum computations, superconductivity, biomedical fields, drug delivery research, magnetic resonance imaging, and organic photovoltaics. Thus, understanding the physics of spectroscopy of these systems, including the influence of the fullerene cage on the behavior of the confined species, and backwards, are matters of great scientific value. Using computer simulations we probe how electrons inside the systems collectively interacts with one another to move internally or to exit, and how much time in attoseconds they consume to reach the detector or for the system itself to thermalize in femtoseconds. How do these information correlate the electronic society in the system? How do the structure of the system play roles in the mechanism? These questions are investigated for both laser and ion impacts. Also, choosing exotic antiparticles like positrons to collide with fullerenes the study of the formation of matter-antimatter transient bound states, the positroniums, is a new direction of our research.