Attosecond and strong-field electron dynamics

5 problems

• Can harmonic spectra measure Berry curvature of a crystal?

  Partially resolved

  In crystals lacking mirror symmetry, electrons pushed by a field also drift sideways because of a geometric property of their bands called Berry curvature. Harmonics polarized at right angles to the laser might read this property out, if other effects can be excluded.

• Why solid-state harmonic models need femtosecond dephasing times

  Contested

  Computer models of harmonic light from crystals only match experiments if the electrons lose their quantum phase within about a femtosecond. That is much faster than measured loss of phase in the same materials, and the cause is not agreed.

• Speed and energy limits of light-field-driven petahertz electronics

  Open

  The electric field of a laser oscillates about a million billion times per second, and it can push currents through solids and nanoscale junctions in step with each oscillation. Whether this can become working logic circuits, and how fast and cheap such switching can be, is unknown.

• Interband versus intraband currents in high-harmonic generation from solids

  Contested

  An intense infrared laser shining on a crystal makes it emit light at many multiples of the laser frequency (high harmonics). Two pictures compete: electrons accelerating within one energy band, or electrons and holes recombining across the band gap.

• Residual gaps between measured and computed atomic photoemission delays

  Partially resolved

  When light knocks an electron out of an atom, the electron leaves a few attoseconds late, and the delay depends on which shell it came from. For some shells the measured delays still differ from the best calculations by more than the error bars.