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@ARTICLE{Rothenbach:866227,
      author       = {Rothenbach, N. and Gruner, M. E. and Ollefs, K. and
                      Schmitz-Antoniak, C. and Salamon, S. and Zhou, P. and Li, R.
                      and Mo, M. and Park, S. and Shen, X. and Weathersby, S. and
                      Yang, J. and Wang, X. J. and Pentcheva, R. and Wende, H. and
                      Bovensiepen, U. and Sokolowski-Tinten, K. and Eschenlohr,
                      A.},
      title        = {{M}icroscopic nonequilibrium energy transfer dynamics in a
                      photoexcited metal/insulator heterostructure},
      journal      = {Physical review / B},
      volume       = {100},
      number       = {17},
      issn         = {0163-1829},
      address      = {Woodbury, NY},
      publisher    = {Inst.},
      reportid     = {FZJ-2019-05393},
      pages        = {174301},
      year         = {2019},
      abstract     = {The element specificity of soft x-ray spectroscopy makes it
                      an ideal tool for analyzing the microscopic origin of
                      ultrafast dynamics induced by localized optical excitation
                      in metal-insulator heterostructures. Using [Fe/MgO]n as a
                      model system, we perform ultraviolet pump/soft x-ray probe
                      experiments, which are sensitive to all constituents of
                      these heterostructures, to probe both electronic and lattice
                      excitations. Complementary ultrafast electron diffraction
                      experiments independently analyze the lattice dynamics of
                      the Fe constituent, and together with ab initio calculations
                      yield comprehensive insight into the microscopic processes
                      leading to local relaxation within a single constituent or
                      nonlocal relaxation between two constituents. Besides
                      electronic excitations in Fe, which are monitored at the Fe
                      L3 absorption edge and relax within 1 ps by electron-phonon
                      coupling, soft x-ray analysis identifies a change at the
                      oxygen K absorption edge of the MgO layers which occurs
                      within 0.5 ps. This ultrafast energy transfer across the
                      Fe-MgO interface is mediated by high-frequency, interface
                      vibrational modes, which are excited by hot electrons in Fe
                      and couple to vibrations in MgO in a mode-selective,
                      nonthermal manner. A second, slower timescale is identified
                      at the oxygen K pre-edge and the Fe L3 edge. The slower
                      process represents energy transfer by acoustic phonons and
                      contributes to thermalization of the entire heterostructure.
                      We thus find that the interfacial energy transfer is
                      associated with nonequilibrium behavior in the phonon
                      system. Because our experiments lack signatures of charge
                      transfer across the interface, we conclude that
                      phonon-mediated processes dominate the competition of
                      electronic and lattice excitations in these nonlocal,
                      nonequilibrium dynamics.},
      cin          = {PGI-6},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {522 - Controlling Spin-Based Phenomena (POF3-522)},
      pid          = {G:(DE-HGF)POF3-522},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000494449700001},
      doi          = {10.1103/PhysRevB.100.174301},
      url          = {https://juser.fz-juelich.de/record/866227},
}