Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

TL;DR

This paper uses analytical R-matrix theory to visualize and analyze hole and spin dynamics in krypton atoms during strong circularly polarized laser ionization, revealing non-adiabatic effects and potential for measuring ionization timing.

Contribution

It introduces a detailed model of hole motion and spin currents in atoms under strong circularly polarized laser fields, highlighting non-adiabatic effects absent in quasistatic theories.

Findings

Hole rotation depends on final energy and electron spin.

Hole motion can be controlled by laser parameters.

Strong-field ionization creates observable spin currents.

Abstract

We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analysing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields [Barth I and Smirnova O 2013 Phys. Rev. A 88 013401]. We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields.