Conservation laws for electron vortices in strong-field ionisation

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Mechanics
• Strong Field Physics

Background:

• Electrons with orbital angular momentum (OAM) are crucial in various physical phenomena.
• Strong laser fields can ionize atoms, leading to complex electron dynamics.
• Understanding electron OAM during ionization is key to controlling quantum states.

Purpose of the Study:

• To develop a theoretical framework for understanding the OAM of twisted electrons during strong field ionization.
• To derive conservation laws for electron OAM under different laser polarizations.
• To provide a new interpretation for above-threshold ionization (ATI) peaks using OAM principles.

Main Methods:

• Formulation of a novel variant of the strong field approximation (SFA).
• Derivation of conservation laws for angular momenta in linearly and circularly polarized fields.
• Analysis of the dependence of photoelectron OAM spectra on laser pulse parameters (e.g., duration, polarization).

Main Results:

• Orbital angular momentum of twisted electrons in linear fields is determined by the magnetic quantum number of the initial state.
• A selection rule for circularly polarized fields is related to ATI peaks, offering a new interpretation.
• Photoelectron OAM spectra are sensitive to laser pulse duration and the parity of laser cycles.

Conclusions:

• The study establishes a theoretical foundation for electron OAM in strong field ionization.
• The findings offer insights into controlling and interpreting electron OAM based on laser properties and initial states.
• This work paves the way for advanced control over electron quantum states in laser-matter interactions.