Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Institut für Physik

Institutskolloquium: Prof. Jan Lüning (Sorbonne Université)

Vortrag zum Thema "Ultrafast Magnetization Dynamics in the light of fs short X-ray pulses"
  • Wann 08.01.2019 von 15:15 bis 17:00
  • Wo Lise-Meitner-Haus, Christian-Gerthsen-Hörsaal, Newtonstraße 15, 12489 Berlin
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Institutskolloquium: Prof. Jan Lüning (Laboratory of Physical Chemistry – Matter and Radiation, Sorbonne Université, Paris) spricht zum Thema "Ultrafast Magnetization Dynamics in the light of fs short X-ray pulses".


With the advent of femtosecond pulsed X-ray sources it has become possible to apply advanced X-ray techniques to the investigation of ultrafast electronic and structural dynamics, a scientific domain for long dominated by all optical pump-probe techniques. The in comparison to visible light significantly shorter wavelength of X-rays enables probing of dynamics with atomic spatial resolution. In addition, due to the inherent element selectivity of resonant X-ray techniques, the dynamics of individual components of complex materials can be probed selectively. In this talk I will discuss how we have exploited these properties of X-ray techniques to investigate ultrafast magnetization dynamics, a phenomenon still poorly understood despite more than 20 years of intense research activities since its discovery in 1996 [1]. Employing resonant magnetic small angle X-ray scattering as probe technique, we have combined femtosecond temporal with nanometer spatial resolution [2,3]. This has enabled us to obtain experimental evidence for the occurrence of spin transport by hot, polarized valence electrons, a phenomenon modeled theoretically in 2010 [4]. Exploiting the coherence of X-ray free electron lasers (XFEL) we have obtained femtosecond time resolved images of the spatial evolution of such laser excitations [5,6]. I will conclude with the presentation of our novel X-ray pulse streaking technique, which allows us to follow the initial magnetization dynamics with a single intense femtosecond short XFEL pulse [7]. This technique, which is applicable to a wide variety of other phenomena, is in particular suited to reveal non-reproducible dynamics in ultrafast phenomena.


Figure: Single X-ray pulse based X-ray streaking of laser induced demagnetization dynamics [7]. The image covers a time window of 1.6 ps. The onset of the pump pulse induced demagnetization dynamics corresponds to the abrupt color change.


[1] E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996).

[2] B. Vodungbo et al., Nature Communications 3, 999 (2012).

[3] B. Pfau et al., Nature Communications 3, 1100 (2012).

[4] M. Battiato et al., Phys. Rev. Lett. 105, 027203 (2010).

[5] T. Wang et al., Phys. Rev. Lett. 108, 267403 (2012).

[6] C. von Korff Schmising et al., Phys. Rev. Lett. 112, 217203 (2014).

[7] M. Buzzi et al., Scientific Reports 7, 7253 (2017).