Attosecond electron dynamics

Observation of electron motion in solids on the attosecond time scale

Propagating electrons in crystals are described as coherent superposition of Bloch states around a central wave vector. Free propagation of Bloch wave packets in crystals, however, is very limited in space and time as elastic and inelastic scattering processes destroy the wave packet’s coherence. Time-resolved photoelectron spectroscopy employing laser pulses with attosecond duration allows for the investigation of Bloch wave packet propagation in conventional crystals.

The principle of attosecond streaking spectroscopy is depicted below.

streaking_schemeAttosecond photoelectron spectroscopy performed on metals covered with a variable number of adsorbate layers provides a time-resolved view on the propagation of Bloch wave packets from the substrate through the adsorbate.

Related publications:

  • C. Lemell, S. Neppl, G. Wachter, K. Tőkési, R. Ernstorfer, P. Feulner, R. Kienberger, and J. Burgdörfer:
    Real-time observation of collective excitations in photoemission.
    Phys. Rev. B 91, 241101(R) (2015), [doi: 10.1103/PhysRevB.91.241101]
  • S. Neppl, R. Ernstorfer, A.L. Cavalieri, C. Lemell, G. Wachter, E. Magerl, E.M. Bothschafter, M. Jobst, M. Hofstetter, U. Kleineberg, J.V. Barth, D. Menzel, J. Burgdörfer, P. Feulner, F. Krausz, and R. Kienberger:
    Direct observation of electron propagation and dielectric screening on the atomic length scale.
    Nature 517, 342 (2015), [doi: 10.1038/nature14094]
  • S. Neppl, R. Ernstorfer, E.M. Bothschafter, A.L. Cavalieri, D. Menzel, J.V. Barth, F. Krausz, R. Kienberger, and P. Feulner:
    Attosecond Time-Resolved Photoemission from Core and Valence States of Magnesium.
    Phys. Rev. Lett. 109, 087401 (2012), [doi: 10.1103/PhysRevLett.109.087401].
  • E. Magerl, S. Neppl, A.L. Cavalieri, E.M. Bothschafter, M. Stanislawski, Th. Uphues, M. Hofstetter, U. Kleineberg, J.V. Barth, D. Menzel, F. Krausz, R. Ernstorfer, R. Kienberger, and P. Feulner:
    A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces.
    Rev. Sci. Instrum. 82, 063104 (2011), [doi: 10.1063/1.3596564].

Control of electron motion in solids with optical fields

In a complimentary experimental approach, collective electron motion, which might be described as highly non-linear polarization, is induced and controlled by the shape of a laser pulse’s electric field. These experiments demonstrate the feasibility of controlling macroscopic currents at optical frequencies.

Related publications:

  • A. Schiffrin, T. Paasch-Colberg, N. Karpowicz, V. Apalkov, D. Gerster, S. Mühlbrandt, M. Korbman, J. Reichert, M. Schultze, S. Holzner, J.V. Barth, R. Kienberger, R. Ernstorfer, V.S. Yakovlev, M.I. Stockman, & F. Krausz:
    Optical-field-induced current in dielectrics.
    Nature 493, 70–74 (2013), [doi: 10.1038/nature11567].
  • A. Schiffrin, T. Paasch-Colberg, N. Karpowicz, V. Apalkov, D. Gerster, S. Mühlbrandt, M. Korbman, J. Reichert, M. Schultze, S. Holzner, J.V. Barth, R. Kienberger, R. Ernstorfer, V.S. Yakovlev, M.I. Stockman, and F. Krausz:
    Addendum: Optical-field-induced current in dielectrics.
    Nature 507, 386 (2014), [doi: 10.1038/nature13077].
  • T. Paasch-Colberg, A. Schiffrin, N. Karpowicz, S. Kruchinin, Ö. Sağlam, S. Keiber, O. Razskazovskaya, S. Mühlbrandt, A. Alnaser, M. Kübel, V. Apalkov, D. Gerster, J. Reichert, T. Wittmann, J.V. Barth, M.I. Stockman, R. Ernstorfer, V.S. Yakovlev, R. Kienberger, and F. Krausz:
    Solid-state light-phase detector.
    Nature Phononics 8, 214 (2014), [doi: 10.1038/NPHOTON.2013.348].