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Theory of Chiral Induced Spin Selectivity
Sakse Dalum1,2, Per Hedegård1
1Niels Bohr Institute , University of Copenhagen , Copenhagen DK-2100 , Denmark.
Nano Letters
|July 3, 2019
Summary
A general theory explains the chiral induced spin selectivity (CISS) effect, showing it relies on nonthermal electrons and molecular degeneracies for spin polarization. Magnetic leads induce magnetization in chiral molecules due to spin-orbit coupling.
Area of Science:
- Condensed Matter Physics
- Quantum Chemistry
- Spintronics
Background:
- The chiral induced spin selectivity (CISS) effect describes spin polarization in chiral materials.
- Experimental CISS effects arise from chiral molecules with small spin-orbit (SO) coupling.
- The nonthermal nature of optically generated electrons is crucial for observable CISS.
Purpose of the Study:
- To present a general theory for the chiral induced spin selectivity (CISS) effect.
- To explain the role of spin-orbit coupling and molecular degeneracies in CISS.
- To investigate the CISS effect in the presence of magnetic leads.
Main Methods:
- Theoretical framework based on the Onsager reciprocal principle.
- Analysis of spin-orbit coupling in chiral molecules with accidental degeneracies.
- Mathematical proof for magnetization induction in a lead adjacent to a magnetic lead.
- Numerical calculations for realistic chiral molecular systems.
Main Results:
- The CISS effect vanishes under thermal averaging but is observable due to nonthermal electrons.
- Accidental degeneracies in molecular spectra lead to significant spin polarization.
- A magnetic lead adjacent to a chiral molecule induces magnetization in the other lead.
- Theoretical predictions are validated by numerical simulations on realistic molecules.
Conclusions:
- A comprehensive theory for the CISS effect is established, highlighting the importance of nonthermal electrons and molecular structure.
- The interplay between spin-orbit coupling and magnetic leads offers new avenues for spintronic device engineering.
- The presented theory provides a robust foundation for understanding and predicting CISS phenomena in chiral systems.
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