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Studying Ultrafast Electron Dynamics in Condensed Matter with Next Gen

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The first generation attosecond light sources were driven by few-cycle near-infrared Ti Sapphire lasers centered at 800 nm. The photon energy of the generated single isolated attosecond pulses are limited to 150 eV. The MURI team demonstrated isolated 53-as pulses with continuous spectra extending to the water window spectral region. The extremely broad bandwidth covers the carbon K-edge and the boron K-edge. The breakthrough was achieved by using a 3 mJ, two-cycle, 1 kHz, carrier envelope phasestable laser source at 1.7 m. A novel scheme for attosecond phase retrieval from noisy streaking traces was developed, which is based on conditional variational generative network. It has the ability to incorporate a complete physics model of the streaking process, and the ability to model the uncertainty of pulse reconstruction in the presence of noise. In-situ methods were introduced as an efficient, all-optical approach to attosecond pulse measurement in which measurement and pulse generation take place simultaneously. While the next generation attosecond light sources are being developed, new physics experiments using the Ti Sapphire based first generation sources have obtained exciting results with solid and water jet targets. A new powerful tool, attosecond transient reflectivity has been demonstrated. Both attosecond transient absorption and attosecond transient reflectivity have been successfully used in investigating the dynamics of core-level excitons in semiconductors and insulators, carrier thermalization and coherent phonon dynamics in metals, as well as coherent magnetism in multi-layer systems. In addition, theoretical study of attosecond optical field control of electron population and symmetry in a two dimensional material silicone, graphene and transition metal dichalcogenides has suggested new schemes to measure fundamental topological properties.

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Technical Report,15 Dec 2014,14 Jun 2020



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