The spinterface mechanism for the chiral-induced spin selectivity effect: A Critical Perspective

TL;DR

The paper critically evaluates the spinterface model as a unifying origin of the chiral-induced spin selectivity (CISS) effect, contrasting it with alternative theories and addressing key criticisms. It argues that CISS arises from a dissipative stabilization of interfacial surface moments induced by chiral electron flow, amplified by spin exchange or SOC, and capable of quantitatively fitting a wide range of experimental data across transport, photoemission, and magnetization phenomena. The authors emphasize the importance of dissipation, explore the limitations and open questions (origin of surface moments, field magnitudes, temperature dependence, and TRS breaking), and propose new predictions, including transport under illumination and thermoelectric CISS, to further test the framework. They conclude that, while not without challenges, the spinterface model currently offers the most coherent, quantitative account of CISS and points toward actionable design principles for chiral-spin devices, with a call for first-principles grounding and broader experimental validation.

Abstract

The chiral-induced spin selectivity (CISS) effect, whereby chiral molecules preferentially transmit electrons of one spin orientation, remains one of the most intriguing and debated phenomena at the interface of spintronics, molecular electronics, and quantum materials. Despite extensive experimental observations across diverse platforms - including transport junctions, photoemission, and enantioselective chemistry - a comprehensive theoretical framework is still lacking. In this perspective, we critically examine the spinterface mechanism as a unifying explanation for the CISS effect. The spinterface model, which hypothesizes a feedback interaction between electron motion in chiral molecules and fluctuating surface magnetic moments, is shown to quantitatively reproduce experimental data across various systems and conditions. We contrast it with some existing theoretical models, highlighting key experimental features. Importantly, we also address open questions and criticisms of this model, including the nature of surface magnetism, the role of dissipation, and the applicability of the mechanism to non-helical or electrode-free systems. By offering falsifiable predictions and reconciling theory with experimental raw data, this work aims to sharpen the dialogue surrounding the microscopic origin of CISS and stimulate further experimental and theoretical progress.

Figures (13)

• Figure 1: I-V curves -- current $J$ in nA as a function of voltage $V$ -- for the two FM magnetization directions for the self-consistent toy model, Eqs. (\ref{['eq:toymodel']}-\ref{['eq:e_shift']}). Electrons move from left to right.
• Figure 2: I-V curves for two directions of FM electrode magnetization, parallel (blue) and anti-parallel (orange) to the direction of current flow. Open symbols are the experimental data (adapted with permission from Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Nano Lett. 2011, 11, 4652–4655. Copyright 2011 American Chemical Society; Ref. Xie11) and solid lines are the theoretical fit to the spinterface model (adapted with permission under a Creative Commons CC BY 4.0 License from Dubi, Y. Spinterface chirality-induced spin selectivity effect in bio-molecules. Chem. Sci. 2022, 13, 10878–10883. Copyright 2022 The Author(s) – Published by the Royal Society of Chemistry; Ref. dubi2022spinterface).
• Figure 3: I-V curves for two directions of FM electrode magnetization, parallel (purple) and anti-parallel (blue) to the direction of current flow. Dots are the experimental data and the solid lines are the theoretical fit to the spinterface model (adapted with permission from Yang, C.; Li, Y.; Zhou, S.; Guo, Y.; Jia, C.; Liu, Z.; Houk, K. N.; Dubi, Y.; Guo, X. Nat. Chem. 2023, 15, 1–8. Copyright 2023 Springer Nature.; Ref. yang2023).
• Figure 4: Experimental data (right panels) and theoretical calculation (left panel) for the CISS polarization, currents and "spin-conductance" of a layer of chiral molecules intercalated between layers of two-dimensional material. The results show excellent quantitative agreement between theory and experiment, and support the claim that the CISS effect is reduced with increasing temperature. (reprinted with permission under a Creative Commons CC BY 4.0 License from Alwan, S.; Sarkar, S.; Sharoni, A.; Dubi, Y. J. Chem. Phys. 159, 014106 (2023). Copyright 2023 The Author(s), published by AIP Publishing; Ref. alwan2023temperature )
• Figure 5: Experimental data (symbols) and theoretical calculation (solid lines) for the I-V measurements of Helicenes on Co nano-islands (data courtesy of the authors of Ref. safari2023spin), for two helical directions. The theory used for the fit is the dynamical spinterface model, which considers the generation of a constant surface magnetization (independent of voltage). Inset: STM image of the chiral molecules on the surface, taken with permission from Ref. safari2023spin. Both the data and the STM image are adapted with permission under a Creative Commons CC BY 4.0 License from Safari, M. R.; Matthes, F.; Schneider, C. M.; Ernst, K.-H.; Bürgler, D. E. Small 2023, 19, 2308233. Copyright 2023 The Author(s), published by Wiley-VCH GmbH. )