Spinterface Mechanism Explains Chiral-Induced Spin Selectivity, Reproducing Experimental Data at Molecular Interfaces

The chiral-induced spin selectivity (CISS) effect, where chiral molecules favour the transmission of electrons with a specific spin, presents a fascinating challenge at the intersection of spintronics and molecular electronics. Subhajit Sarkar from the Shiv Nadar Institution of Eminence, Amos Sharoni from Bar Ilan University, and Oliver L. A. Monti from the University of Arizona, alongside Yonatan Dubi and colleagues, now present a critical examination of the ‘spinterface’ mechanism as a potential explanation for this phenomenon. Their work offers a unifying theoretical framework that quantitatively matches experimental observations across a range of systems and conditions, addressing a long-standing gap in the field. By contrasting this model with existing theories and tackling key criticisms regarding surface magnetism and energy dissipation, the team provides falsifiable predictions and aims to stimulate further progress in understanding the microscopic origins of CISS.

Chirality Filters Electron Spin Selectivity

This extensive research explores chirality-induced spin selectivity (CISS), the ability of chiral molecules to preferentially transmit electrons with a specific spin orientation, holding significant potential for advancements in molecular electronics and spintronics. The core of CISS lies in how chiral molecules influence electron spin, acting as filters that favor one spin orientation over another, with potential applications in molecular spintronics, electrocatalysis, chiral photodiodes, and advanced materials. Central to studying CISS is creating single-molecule junctions, where individual molecules form electronic circuits, characterized by transition voltage spectroscopy, and utilizing carbon nanotubes as scaffolds for functional networks, alongside theoretical modeling using quantum mechanical calculations. Researchers are also exploring the influence of microwave fields on electron transport and utilizing quantum interference effects to enhance device performance. Despite significant progress, challenges remain in fully understanding and controlling CISS, including the precise mechanism driving the effect and methods to precisely control spin selectivity. Creating stable, reproducible devices based on chiral molecules and scaling up production for practical applications also present ongoing research areas, promising to revolutionize electronics and materials science.

Spinterface Model Explains Chiral Spin Selectivity

Scientists are investigating the chiral-induced spin selectivity (CISS) effect, where chiral molecules preferentially transmit electrons with a specific spin, by developing the spinterface model. This model proposes a feedback interaction between electron movement within chiral molecules and fluctuating magnetic moments on a surface, successfully reproducing experimental data across diverse systems. Researchers modeled electron transport through chiral molecules, focusing on how molecular structure influences spin polarization, and found that structural chirality does not automatically equate to electron chirality. To define a chiral electronic system, the team proposed that such a system exhibits a magnetic field parallel to the average current, developing computational methods to explore conditions under which such a field could be generated, even in non-helical chiral molecules. Employing a single-level transport model within a dynamic spinterface approach, they incorporated stable surface magnetic moments that shift energy levels, revealing that the temperature dependence of CISS is not universal and varies depending on the specific system. Understanding a system’s transport properties is crucial for deciphering the temperature dependence of the observed CISS effect, providing a detailed theoretical and computational framework for understanding and predicting CISS, paving the way for further exploration of spin-based electronics and chiral materials.

Spinterface Mechanism Explains Chiral Spin Selectivity

This research presents a comprehensive examination of the chiral-induced spin selectivity (CISS) effect, where chiral molecules preferentially transmit electrons with a specific spin orientation. The team critically assessed the ‘spinterface’ mechanism, proposing it as a unifying explanation for CISS, and demonstrated its ability to quantitatively reproduce experimental data across diverse systems, successfully accounting for observed experimental features. The work not only provides physical intuition regarding the CISS effect but also offers a quantitative description of the effect and qualitative explanations for various experimental observations, proposing several testable predictions, including the expected reduction of CISS in molecules connected to electrodes via non-chiral components, a reversal of spin roles when using tantalum electrodes instead of gold, and a detectable signature in photoemission experiments when tilting the detector. Recognising that, like all models, the spinterface approach is not perfect, future work should focus on developing a microscopic model to predict the coupling parameters within the spinterface model, representing a significant step towards understanding the microscopic origins of CISS and providing a framework for guiding future experimental and theoretical investigations.