Ultrafast phenomena in surfaces observed with time-resolved surface science techniques:
the LaserLab of the group of Prof. J. Osterwalder.

Introduction
These projects aim at observing ultrafast processes and measuring timescales of relaxation processes which occur in solid surfaces. The typical timescales of so-called ultrafast processes lies in the range of picoseconds down to attoseconds. Such measurements are carried out in pump-probe mode. In small-scale "table-top" experiments, femtosecond light pulses produced by mode-locked laser oscillators are used as pump and probe pulse: A femtosecond laser pulse output from such an oscillator is split into two parts creating thereby two pulses which are perfectly synchronized. One pulse is utilized to trigger the ultrafast process by promoting electrons from the ground state into excited states ("pump"). From there the whole system evolves towards thermodynamic equilibrium. The second pulse ("probe") serves to measure some quantity of interest in a well-defined moment after the pump pulse. Assembling the results of these probe measurements as function of time delay between pump and probe, one obtaines a stroboscopic movie of the transient state of the system.
From the above it is clear that the precision of the measurements or the temporal resolution depends on the temporal width of pump and probe pulses: the shorter the pulses the more precisely the fast timescales can be extracted from the data. We use a commercial femtosecond laser system which consists of a Kerr-lens mode-locked laser oscillator, a regenerative pulse amplifier, and a parametric amplifier. Typical pulse energies are 5 nJ, 4 µJ, and 70 nJ, respecively with repetition rates of 76 MHz (oscillator) and 100-250 kHz (amplifiers).

Projects

Current research projects:

  • Electron transfer and structural dynamics of molecules within the NCCR MUST
  • Time-resolved photoelectron spectroscopy (2PPE):
    • self-assembled molecular layers (like e.g. diamondoids)
    • surface systems with strong spin-orbit coupling
    • ultrafast magnetization dynamics
    • insulating boron nitride monolayers
  • Development of a source for spin-polarized electrons

Previous projects:

  • Photo-induced field emission from tungsten tips (now at ETH Zürich in the framework of the ambizione grant of Hirofumi Yanagisawa
  • Time-resolved low-energy-electron diffraction

Open positions

Post-doctoral positions

There is currently no position available.

Ph.D. students:

There is currently no position available.

General requirements are a diploma or master in physics in the field of solid state physics or femtosecond pump-probe experiments and good experimental skills. Knowledge of vacuum technology and/or optical setups are an asset.

If you are interested, please, contact Prof. J. Osterwalder or Dr. M. Hengsberger. Further open positions in our group can be found on this page.

Practical work for students:

  • Semesterarbeiten, Forschungspraktika: duration ca. 1-2 months
  • Bachelorarbeit : duration about 10 weeks
  • Masterarbeit: duration 9 months
Please, contact directly one of the persons indicated below.

Such work usually consists of small independent projects like characterization of laser pulses (spectrum, temporal width), film growth or the setup of small experimental tools. It always includes the writing of a small report. The master thesis consists usually of a research project involving surface physics in ultrahigh vacuum systems and the femtosecond laser system.


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People in the LaserLab
    Luca Castiglioni    Ph.D., post-doc
    Dominik Leuenberger    Ph.D. student
    Michael Greif    Ph.D. student
    Colette Janssen    master student
    Eveline Eisenring    master student
    Patrick Donà    bachelor student
    Matthias Hengsberger    Ph.D., senior research assistant

...and other people, partially involved, who are listed under different projects:
contact information can be found on the sites of the group or of the institute.

The LaserLab is located in building Y36 at Irchel Campus of the University of Zurich.

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Publications
  1. D. Leuenberger, H. Yanagisawa, S. Roth, J. Osterwalder, and M. Hengsberger,
    Disentanglement of electron dynamics and space-charge effects in time-resolved photoemission from h-BN/Ni(111),
    Phys. Rev. B 84, 125107 (2011).
  2. H. Yanagisawa, M. Hengsberger, D. Leuenberger, M. Klöckner, C. Hafner, T. Greber, and J. Osterwalder,
    Energy distribution curves of ultrafast laser-induced field emission and their implications for electron dynamics,
    Phys. Rev. Lett. 107, 087601 (2011); cond-mat: arXiv.1103.4310.
  3. L. Castiglioni, M. Greif, D. Leuenberger, S. Roth, J. Osterwalder, and M. Hengsberger,
    Time-resolved photoelectron spectroscopy to probe ultrafast charge transfer and electron dynamics in solid surface systems and metal-molecule interfaces,
    Chimia 65, 342 (2011).
  4. S. Roth, D. Leuenberger, J. Osterwalder, J.E. Dahl, R.M.K. Carlson, B. Tkachenko, A.A. Fokin, P.R. Schreiner, and M. Hengsberger,
    Negative-electron-affinity diamondoid monolayers as high-brilliance source for ultrashort electron pulses,
    Chem. Phys. Lett. 495, 102 (2010).
  5. M. Hengsberger, D. Leuenberger, and S. Roth,
    Modengekoppelete Laser - (Im-)Pulse für die Forschung,
    Bulletin SEV/VSE Electrosuisse 6/2010; reprint: pdf (1.2 MB).
  6. H. Yanagisawa, C. Hafner, P. Donà, M. Klöckner, D. Leuenberger, T. Greber, J. Osterwalder, and M. Hengsberger,
    Laser-induced field emission from a tungsten tip: optical control of emission sites and the emission process,
    Phys. Rev. B 81, 115429 (2010).
  7. H. Yanagisawa, C. Hafner, P. Donà, M. Klöckner, D. Leuenberger, T. Greber, M. Hengsberger, and J. Osterwalder,
    Optical control of field-emission sites by femtosecond laser pulses,
    Phys. Rev. Lett. 103, 257603 (2009).
  8. C. Cirelli, M. Hengsberger, A. Dolocan, H. Over, J. Osterwalder, and T. Greber
    Direct observation of space-charge dynamics by picosecond low-energy electron scattering,
    Europhys. Lett. 85, 17010 (2009);
    cond-mat: arXiv.0807.0582.
  9. M. Hengsberger, F. Baumberger, H.J. Neff, T. Greber, and J. Osterwalder,
    Photoemission momentum mapping and wavefunction analysis of surface and bulk states on flat Cu(111) and stepped Cu(443) surfaces: a two-photon photoemission study,
    Phys. Rev. B 77, 085425 (2008).
  10. M. Muntwiler, M. Hengsberger, A. Dolocan, H.J. Neff, T. Greber, and J. Osterwalder
    Energetics and dynamics of unoccupied electronic states in the h-BN/Ni(111) interface,
    Phys. Rev. B 75, 07407 (2007).
  11. A. Dolocan, M. Hengsberger, H.J. Neff, C. Cirelli, M. Barry, T. Greber, and J. Osterwalder,
    Electron-light correlator in a metal pinhole,
    Jap. J. Appl. Phys. 45, 285 (2006).
  12. M. Hengsberger, M. Muntwiler, T. Greber, and J. Lobo-Checa,
    Source for spin-polarized electrons, (300 kB, pdf)
    US-provisional patent (filed July 13, 2005).
    US patent no. WO 2007/006168 (filed July 2006).
  13. R. Karrer, H.J. Neff, M. Hengsberger, T. Greber, and J. Osterwalder,
    Design of a miniature picosecond electron gun for time-resolved electron scattering experiments,
    Rev. Sci. Instr. 72, 4404 (2001).

The complete publication list of the group can be found here.
Preprint versions of the papers published in 2008 or later can be obtained from the Open Access Repository of the University of Zürich ZORA.


Financial support
  • Swiss National Science Foundation
  • Swiss National Science Foundation through National Center of Competence in Research MUST
  • Research Foundation of the University of Zurich

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last update: mh 09/09/2011