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High temperature superconductors and Mott insulators far from equilibrium conditions - Luca Perfetti

Ecole Polytechnique

This seminar covers our recent results on the dynamics of correlated materials upon strong photoexcitation by short laser pulses. The ultrafast temporal evolution of superconducting Bi2Sr2CaCu2O8+x is investigated by time resolved photoelectron spectroscopy and Time Resolved THz spectroscopy. I show that high temperature superconductors far from equilibrium display and an exotic state in which phase coherence, pairing amplitude and electronic dissipation are not proceeding on equal footing. In the second part of the seminar, I discuss the temporal evolution of electronic states in strontium iridate Sr2IrO4. The surprising outcome is that photoexcited holon-doublon pairs decay in to midgap states on an ultrafast timescale. Presumably, this behavior arises from emission of collective excitations and defect mediated decay. We report identical relaxations in intrinsic and doped compounds, suggesting that metallicity and screening do not influence the relaxation of the photoexcited electrons. Our time resolved photoemission data of iridates are in good agreement with optical experiments on copper oxides, providing compelling evidence of common dynamics in these two dimensional Mott insulators with strong antiferromagnetic correlations.


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