Refreshments are served at 2:30 p.m. outside Room 016.
Dr. Ofer Kedem, Center for Bio-Inspired Energy Science, Northwestern University
“Electron Ratchets: Producing Currents Without a Bias”
Biological motors, such as the myosin-actin system responsible for muscle contraction, rectify Brownian motion using asymmetry and chemical energy. This type of rectification mechanism is called a ratchet, and has been implemented in artificial systems. Generally, ratchets are nonequilibrium devices producing directed transport without an overall applied bias. Ratchets operate by breaking time-reversal and spatial symmetries through the application of a timedependent potential with locally asymmetric features. In this talk, I will highlight some of our recent explorations of electron ratchets, using both theory and experiment. We find complex, unintuitive behaviors, with high sensitivity to structural and operating parameters, which lead to effects such as current reversals. I will detail some promising features of a new experimental ratchet design; a new understanding of the relation between temporal and spatial symmetry in the mechanism; as well as a proposed photovoltaic device based on the ratchet principle.
Ofer Kedem is a postdoctoral fellow at the Center for Bio-inspired Energy Science, advised by Prof. Emily A. Weiss. He received a B.Sc. degree in Chemistry from Tel Aviv University, and a M.Sc. and Ph.D. from the Weizmann Institute of Science, where he studied with Prof. Israel Rubinstein. During his studies, he experimentally explored the interaction of plasmonic nanoparticle films with dielectric and fluorescent materials, mainly in a sensing context. His current work is on electron ratchets, non-equilibrium devices that generate current as a dynamic steady-state, without using a bias.