Low-Resistance Molecular Wires Propagate Spin-Polarized Currents

Area of Science:

• Organic spintronics
• Molecular electronics
• Chirality-induced spin selectivity (CISS) effect

Background:

• Traditional spintronics relies on inorganic ferromagnetic materials and electrodes for spin injection.
• The CISS effect in chiral organic molecules offers a new paradigm, enabling spin filtering without magnetic electrodes.
• Previous CISS effect studies were limited to molecular insulators.

Purpose of the Study:

• To investigate if achiral molecular wires can transmit spin-polarized currents generated by the CISS effect.
• To explore the role of molecular wire conjugation length in preserving spin polarization.
• To demonstrate spin current propagation over molecular distances exceeding the chiral moiety.

Main Methods:

• Fabrication of self-assembled monolayers (SAMs) combining chiral molecules (l-proline)8 (Pro) with achiral (porphinato)zinc (PZn) molecular wires.
• Interrogation using magnetic conducting atomic force microscopy (mC-AFM).
• Evaluation via spin-dependent electrochemistry and spin Hall devices.

Main Results:

• Achiral molecular wires successfully transmit spin-polarized currents initiated by the CISS effect.
• Measured spin polarizability increased with the conjugation length of the achiral PZn component.
• Spin-polarized currents propagated without dephasing over distances longer than the chiral Pro moiety.

Conclusions:

• Chiral molecules are not essential for transmitting CISS-generated spin-polarized currents.
• Achiral molecular wires can preserve spin polarization, enabling spin current transmission over extended molecular lengths.
• This work expands the potential of organic materials in spintronics by demonstrating long-range spin transport.