Treating Branch Cuts in Quantum Trajectory based Electron Holography
April 30th, 2019 ANDY MAXWELL UCL London’s Global University

Electron holography in above threshold ionisation (ATI), promises the imaging of an atom or molecule using it’s own the freed electron. This exploits the interference of different paths that the electron can take to the detector. These results have motivated the development of models based on electron pathways (known as quantum trajectory models) that include the Coulomb interaction, going beyond the SFA and similar approaches. Quantum trajectory models must use complex valued trajectories throughout to fully account for all physical effects and to remain analytic. However, this leads to a dire consequences, namely, branch cuts due to the multivalued square root in the Coulomb potential. These are discontinuous lines that if crossed by the temporal integration contour cause defects in the final momentum dependent probability distribution. A solution to this issue has proposed, which modifies the complex integration contour for each value of momentum. This solution works well for models that include the Coulomb phase, but cannot be used for models that also consider the Coulomb force on the trajectories.

We present an alternative method that accounts for the branch cuts by adding corrections to the standard contour and apply it exactly to models with Coulomb phase and approximately to the CQSFA that includes the Coulomb force. We find in both cases fringe dislocation defects in the momentum distributions caused by branch cuts can be completely removed. We also investigate the link between recolliding trajectories and branch cuts and how crossing some branch cuts correspond to a hard collision.

Seminar, April 30, 2019, 15:00. ICFO’s Seminar Room

Hosted by Maciej Lewenstein