2007 Alfvén Lecture: Complex Plasmas - a new state of matter with unusual properties

“Complex plasmas” (consisting of electrons, ions and charged microparticles) represent a new and quite unusual state of soft matter – a state that until its discovery was believed impossible to exist.

In this talk, first the main properties of this new system are summarised. Then some specific results of dedicated experiments will be presented, including new insights into the fundamental stability principles of condensed matter, the onset of cooperative phenomena in strongly coupled systems, the pathways to equilibrium in interacting flowing plasmas, the first observation of the onset of turbulence at the individual particle (kinetic) level and critical phenomena (phase transitions) viewed also at the kinetic level. Due to the comparatively large mass of the microparticles (several 10’s of billion atomic masses) all dynamical processes are slowed down so that they can be viewed in real time. The large particle mass also implies that some key experiments have to be performed in space under microgravity conditions.

The talk finishes with an outlook into future topics of interest in this young and expanding field.