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O: Fachverband Oberflächenphysik

O 68: Focus Session: Non-equilibrium Dynamics in Light-driven Materials: Theory Meets Experiment

O 68.4: Hauptvortrag

Mittwoch, 22. März 2017, 12:00–12:30, TRE Phy

Ultrafast Terahertz and XUV ARPES Probes of Quantum Materials Dynamics — •Robert A. Kaindl — Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, USA

In this talk I will discuss the application of ultrashort light pulses - from THz to Extreme-UV - to the study of vibrational coupling and emergent correlations in quantum materials. Transition-metal oxides, in particular, exhibit an intriguing self-organization of charges into nanoscale "stripes", whose driving forces and role in high-Tc superconductivity remain unresolved. We will first present transient multi-THz and mid-IR experiments that capture the initial steps of vibrational symmetry breaking and charge ordering in stripe-phase nickelates, indicating the precursor role of charge localization and exposing the electronic and structural coupling dynamics [1]. In the second part, I will discuss our development of ultrafast angle-resolved photoemission spectroscopy (ARPES) with extreme-ultraviolet (XUV) pulses at 50-kHz repetition rate, and its application to sensitively access electronic dynamics of quantum materials across momentum space [2]. Studies of semiconducting and correlated dichalcogenides access the crossover of light-induced perturbation and melting of charge density waves and provide evidence for excitonic signatures in ARPES spectra. [1] G. Coslovich, et al. Nature Comm. 4, 2643 (2013); arXiv:1603.07819 (2016). [2] H. Wang, et al. Nature Comm. 6, 7459 (2015); J. H. Buss, et al. in preparation (2016).