In this project the spin and magnetization dynamics of ferromagnetic and antiferromagnetic thin films will be studied on the nanometer length scale. Femtosecond time-resolved photoemission electron microscopy (tr-PEEM) with back-side pumping, front-side probing geometry will be applied in combination with time-resolved two-photon photoelectron spectroscopy (tr-2PPE). With independently tunable pump and probe laser pulse wavelengths, we will address the spatial distribution of spin dynamics driven by a transient electronic structure. This transient electronic structure under investigation will be excited indirectly by a spin current or directly by optical pulses. These excitations will be investigated by tr-2PPE and spatially tailored by plasmonic nanostructures in the tr-PEEM experiments. A specific goal is to image domain switching and domain wall motion in ferromagnetic and antiferromagnetic thin films on the nanometer scale upon femtosecond spin and optical excitations.

Publications (1^st Funding Period 2018 - 2021)

• Plasmonic spin-Hall effect of propagating surface plasmon polaritons in Ni₈₀Fe₂₀ microstructures 
  M. Paleschke, C.-T. Chiang, L. Brandt, N. Liebing, G. Woltersdorf, and W. Widdra
  New J. Phys. 23, 093006 (2021)  - DOI: 10.1088/1367-2630/ac1c83

• Exchange-striction driven ultrafast nonthermal lattice dynamics in NiO  
  Y. W. Windsor, D. Zahn, R. Kamrla, J. Feldl, H. Seiler, C.-T. Chiang, M. Ramsteiner, W. Widdra, R. Ernstorfer, and L. Rettig
  Phys. Rev. Lett. 126, 147202 (2021)  - DOI: 10.1103/PhysRevLett.126.147202

• Imprinting photon orbital angular momentum during laser-assisted photoemission from quantum wells 
  J. Wätzel, A. Blättermann, D. Schulz, C.-T. Chiang, and J. Berakdar 
  Opt. Lett. 45, 5970 (2020)  - DOI: 10.1364/OL.409206

• Ultrafast coupled charge and spin dynamics in strongly correlated NiO 
  K. Gillmeister, D. Golež, C.-T. Chiang, N. Bittner, Y. Pavlyukh, J. Berakdar, P. Werner, and W. Widdra 
  Nat. Commun. 11: 4095 (2020)  - DOI: 10.1038/s41467-020-17925-8

• Laser-based double photoemission spectroscopy at surfaces 
  C.-T. Chiang, A. Trützschler, M. Huth, R. Kamrla, F. O. Schumann, and W. Widdra 
  Prog. Surf. Sci. 95, 100572 (2020)  - DOI: 10.1016/j.progsurf.2020.100572

• SiO₂/Si(001) studied by time-resolved valence band photoemission at MHz repetition rates: Linear and nonlinear excitation of surface photovoltage
  R. Kamrla, A. Trützschler, M. Huth, C.-T. Chiang, F. O. Schumann, and W. Widdra
  J. Vac. Sci. Technol. A 37, 021101 (2019)  - DOI: 10.1116/1.5082188

• Extended energy range analysis for angle-resolved time-of-flight photoelectron spectroscopy
  M. Huth, A. Trützschler, C.-T. Chiang, R. Kamrla, F. O. Schumann, and W. Widdra
  J. Appl. Phys. 124, 164504 (2018)  - DOI: 10.1063/1.5048515