2013 Physics Colloquium
Probing nonequilibrium electron-phonon
dynamics in Mott insulator and
charge-density waves using
ultrafast electron crystallography
Chong-Yu Ruan
Department of Physics and Astronomy, Michigan State
University, East Lansing, MI 48824
The coexistence of various electronic and structural phases that
are close in free-energy is a hallmark in strongly correlated
electron systems, where fascinating properties, such as metal-insulator transition, colossal
magnetoresistance, and high-temperature superconductivity, can be induced often
interchangeably by applying heat, stress, electric field, or charge carrier doping. The
collective phase behavior under these tuning parameters can involve strongly cooperative
electronic and structural modifications in the ordered state, hence deciphering the
fundamental driving mechanism in such systems remains very active in condensed matter
physics. I will outline the recent results of metal-insulator transition in vanadium dioxide
and charge melting transition in 2D charge-density waves by various experiments and
theories, including the nonequilibrium electron dynamics unveiled by ultrafast
photoemission studies exclusively sensitive to the electronic order parameter. I will also
describe the most recent findings from ultrafast electron crystallography, which provide
crucial structural aspects to correlate lattice dynamics with electronic evolutions to address
the two sides of a coin in the ultrafast switching of a cooperative state. These new results
shed light on several controversial issues and bring forth new perspectives in
understanding light-matter interactions in strongly correlated systems with many potential
applications.
4:00 pm on January 31, 2013
245 Physics Building
Refreshment starts 3:45 pm