Physics Colloquium: Ultrafast dynamical processes in quantum materials.

Prof. Ioannis Chatzakis, Texas Tech University

Abstract:  Low-dimensional (e.g., atomically thin) continues to gain prominence in applications ranging from electronics to photonics and energy conversion systems. Critical to efficiently developing these systems is the understanding of the fundamental processes related to the dynamics of charge carriers, phonons, and other excitations (i.e. excitons, polaritons). Understanding the principles that govern these excitations will enable the fabrication of optoelectronic and photonic devices with novel and enhanced functionalities. While significant studies of nanomaterials, optical, and electrical transport properties are often made, identifying the mechanisms and timescales governing the interactions between electrons, phonons, and other excitations can be extremely challenging. I will discuss how excited carriers in low-dimensional systems undergo energy relaxation through various dynamical processes that occur over different time scales. Various physical mechanisms such as electron-phonon interactions, phonon-phonon interactions, and carrier recombination are involved in these processes. The electron–phonon scattering processes are essential to understanding and controlling the energy and charge flow in electronic and energy conversion devices. For this study, we used time-resolved pump-probe spectroscopy with sub-picosecond resolution to observe charge carrier dynamics in bilayer graphene.

Bio: Dr. Ioannis Chatzakis earned his Ph.D. in Physics from Kansas State University in Dec. 2009. After completing his coursework, he moved to Columbia University to work on the optical and electronic properties of carbonic materials under the supervision of Prof. Tony F. Heinz. He also holds an M.Sc. degree in Physical Chemistry (Applied Molecular Spectroscopy), and a B.Sc. degree in Electrical Engineering. Before joining TTU, he was an American Society for Engineering Education (ASEE) research fellow residing at the U.S. Naval Research Laboratory (NRL) in Washington, DC. Prior to the NRL appointment, he trained as a postdoctoral researcher at Iowa State University/Ames Laboratory, Stanford University, and the University of Southern California (USC). He is a member of the American Physical Society, Materials Research Society, and Optical Society of America, and he serves the community as a referee in several scientific journals.