CPM Seminar

Amplitude and Phase Dynamics in a Photo-induced Charge Density Wave Transition

Anshul Kogar

MIT

Upon excitation with an intense ultrafast laser pulse, a symmetry-broken ground state can undergo a non-equilibrium phase transition through pathways dissimilar from those in thermal equilibrium. Determining the mechanism underlying these photo-induced phase transitions has been a long-standing issue in the study of condensed matter systems. I will talk about our investigation of the light-induced melting of a unidirectional charge density wave (CDW) material, LaTe3. Using a suite of time-resolved probes, we independently track the amplitude and phase dynamics of the CDW. We find that a quick (1 ps) recovery of the CDW amplitude is followed by a slower reestablishment of phase coherence. This longer timescale is dictated by the presence of topological defects: long-range order (LRO) is inhibited and is only restored when the defects annihilate. Our results provide a framework for understanding other PIPTs by identifying the generation of defects as a governing mechanism.