CPM Seminar

Resolving microscopic dynamics in condensed matter with ultrafast THz spectroscopy

Jean-Michel Ménard

University of Ottawa

Broadband electro-optic detection of light in the infrared spectral range provides unique access to low-energy microscopic dynamics. Fascinating physical phenomena in various materials can then be investigated with this optical technique also referred to as time-resolved terahertz (THz) spectroscopy. In a first project, we trace the matter component of a cooling exciton-polariton gas inside a semiconductor microcavity, and observe, for the first time, the build-up process leading to Bose-Einstein condensation 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 [1]. In a second project, we investigate highly correlated materials exhibiting intriguing phase transitions during the photo-induced melting and recovery processes of their 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 such as superconductivity [2]. Finally, we propose an approach to make an all-fiber THz device for time-resolved spectroscopy applications by inducing phase-matched second-order nonlinear optical effects in a gas-filled hollow-core photonic crystal fiber (PCF). The basic concept is demonstrated by detecting electric-field-induced second harmonic in a xenon-filled kagomé PCF [3].

[1] J.-M. Ménard, C. Poellman, M. Porer, E. Galopin, A. Lemaître, A. Amo, J. Bloch, and R. Huber. Revealing the dark side of a bright exciton-polariton condensate, Nat. Commun. 5, 4648 (2014)
[2] M. Porer, U. Leierseder, J.-M. Ménard, H. Dachraoui, L. Mouchliadis, I. E. Perakis, U. Heinzmann, J. Demsar, K. Rossnagel and R. Huber. Non-thermal separation of electronic and structural orders in a persisting charge density wave, Nat. Mater. 13, 857 (2014)
[3] J.-M. Ménard, F. K�ttig and P. St.J. Russell. Broadband electric-field-induced LP01 and LP02 second harmonic generation in Xe-filled hollow-core PCF, Opt. Lett. 41, 3795 (2016)