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IMM colloquium October 23: "See atoms move in real time: ultrafast electron diffraction" (Lecture)

Tuesday 23 October 2018Add to my calendar
from 16:00
prof. Petra Rudolf (Zernike Institute for Advanced Materials, RUG)
Preceding lecture
Salvatore Licciardello (HFML), title: "Electrical resistivity across a Nematic quantum critical point"

prof. Petra RudolfTime-resolved electron diffraction is a unique tool for providing direct and detailed information on the structural dynamics of solid surfaces, nano-sized materials, molecules and atomically thin layers, thanks to the high cross section for interaction between electron and matter. Femtosecond lasers are used to generate ultrashort light and electron pulses. Light initiates a process in the sample - a phase transition, an electronic excitation or simply a temperature jump - and by recording snapshots of the electrons diffracted from the sample in a stroboscopic fashion, one can image the photo-induced motion of the structure.

In this talk I shall try to give a taste of the immense possibilities of ultrafast electron diffraction, illustrating how this novel technique opens the door to physical understanding of many aspects of light-matter interaction such as out of equilibrium structural phase transitions, heat transport through interfaces and the creation of coherent phonons. Specific examples that will be discussed are the martensite to austenite phase transition in a Ni-Mn-Ga foil, which is a magnetic shape memory Heusler alloy, and the structural dynamics of a Cr/Au bi-layer foil after photo-excitation by a near-infrared femtosecond laser pulse. For the latter we directly followed atomic disorder caused by the generation of hot electrons, the subsequent transfer of energy to phonons and the diffusion of both electrons and phonons through the Cr/Au interface. For the Heusler alloy instead, after the initial change of the material from the low temperature martensite phase to the high temperature austenite phase, oscillations are observed, indicating a strong tendency in the lattice to go back to the low-temperature martensite phase.

dr. Britta Redlich