Mixed Quantum-Classical Approaches to Spin Current and Polarization Dynamics in Chiral Molecular Junctions

Area of Science:

• Molecular spintronics
• Quantum transport phenomena
• Chiral-induced spin selectivity (CISS)

Background:

• Chiral molecular junctions enable spin filtering without magnetic fields.
• Understanding spin dynamics in these systems is crucial for spintronics.
• Electron-phonon coupling significantly influences molecular electronic properties.

Purpose of the Study:

• Investigate spin transport in chiral molecular junctions.
• Explore the role of electron-phonon coupling on spin dynamics.
• Compare quantum master equation (QME) with surface hopping (SH) and mean-field Ehrenfest (MF) methods.

Main Methods:

• Combined QME for electronic dynamics with SH and MF for electron-phonon coupling.
• First-time application of SH for spin dynamics in molecular junctions.
• Analysis of transient spin polarization under varying bias, molecular length, and spin-orbit coupling (SOC).

Main Results:

• Transient spin polarization was observed but ultimately vanished.
• Bias, molecular length, and SOC were identified as key dynamic factors.
• Electron-phonon coupling modulated current-voltage responses, enhancing current at moderate bias and suppressing it at high bias.

Conclusions:

• SH method is suitable for low-frequency vibrations and weak coupling, outperforming MF.
• The interplay between electronic and vibrational effects on CISS requires further investigation.
• Findings provide insights into molecular spintronics and guide future research.