Attosecond Charge Migration Can Break Electron Symmetry While Conserving Nuclear Symmetry

Area of Science:

• Quantum chemistry
• Attosecond science
• Molecular dynamics

Background:

• Charge migration involves ultrafast electron transfer within molecules (attoseconds to femtoseconds).
• During this process, nuclear positions remain essentially constant, preserving nuclear symmetry.
• However, electron movement can lead to spatial symmetry breaking of electron density.

Purpose of the Study:

• To theoretically demonstrate how attosecond charge migration can break electron density symmetry.
• To show this occurs despite conserved nuclear framework symmetry.
• To provide proof-of-principle examples.

Main Methods:

• Theoretical modeling of electron dynamics.
• Preparation of electrons in coherent superpositions of nondegenerate electronic states.
• Analysis of symmetry transformations in molecular systems.

Main Results:

• Attosecond charge migration breaks electron density spatial symmetry when electrons are in a coherent superposition of states with different irreducible representations.
• Demonstrated in H₂⁺ cation (D_∞h → C_∞v) and H₂O molecule (C_2v → C_s).
• Periodic charge migration observed in these systems.

Conclusions:

• Electron symmetry breaking is achievable via attosecond charge migration.
• This phenomenon highlights a unique interplay between electron dynamics and molecular symmetry.
• Provides a pathway for controlling molecular electronic properties at the ultrafast timescale.