Ultrafast THz mapping of dynamical polaritonic systems and charge density waves

21.01.2014, 14:00

Dr. Jean-Michel Ménard, Institut für Experimentelle und Angewandte Physik, Universität Regensburg

Ultrabroadband electro-optic detection of light in the infrared spectral range provides unique access to low-energy dynamics. As a result, fascinating physical phenomena in various materials can be investigated with this optical technique also referred to as time-resolved THz spectroscopy. In a first project, we trace the matter component of a cooling exciton-polariton gas, and observe, for the first time, the build up process leading to a Bose-Einstein condensate in solid state. Our measurements establish a fundamental difference between polariton and photon lasing and open novel possibilities for coherent control of a macroscopic quantum sate. Second, we map out a large photonic bandgap in a one-dimensional photonic crystal which is introduced by activating ultrastrong light-matter coupling on a sub-cycle scale. The results pave the way towards non-adiabatic quantum electrodynamics effects analogous to Hawking radiation of black holes. Finally, highly correlated materials exhibiting intriguing ordered states, such as superconductivity or charge density wave, are investigated during the photo-induced melting and recovery processes of the microscopic ordering. We disentangle electronic and lattice parameters and trace the evolution of a new transient phase of matter which could be used to elucidate a broad class of phase transitions.