Wed, 16.12.2020  |  14:00
Virtual, via Zoom link

Ultrafast lattice, electron and spin dynamics through coherent “soft mode driving”

Dr. Urs Staub | Paul Scherrer Institut

talks about

The ultrafast dynamics of condensed matter systems has been increasingly studied with optical-probe experiments in the last decade. Very recently, the availability of ultrashort X-ray pulses to probe electronic, magnetic and structural dynamics have dramatically increased due to the built up of X-ray Free Electron Lasers such as SwissFEL, Eu-XFEL and PAL.


In this presentation I like to summarize our efforts in using low cycle THz pulses to drive “soft modes” in correlated electron materials and probe the materials response with fs X-ray pulses. X-rays have the sensitivity to selectively probe the structural, the magnetic or the electronic response of the systems. I will first concentrate on an experiment, in which we excite the polar soft mode and study the ultrafast time dynamics of the lattice by X-ray diffraction. It shows that the coherent excitation leads to a phonon upconversion based on the anharmonicities in the chemical potential.[1] Then I present first preliminary SwissFEL results on the ultrafast structural dynamics of a low-dimensional defect structure, which is deeply buried at an interface. By using the analogy of our work on an electromagnon excitation [2], I will present first results from SwissFEL of a coherent orbital excitation (an electro-orbiton) and its induced dynamics in a quantum magnetic titanate material.      


[1] M. Kozina et al., Nature Phys. 15, 387 (2019).

[2] T. Kubacka et al., Science 343,1333 (2014).

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