Recent research at Johannes Gutenberg University Mainz (JGU) has demonstrated a novel approach to controlling electron spin using chiral molecules, potentially revolutionizing electronic technology. While electrons are commonly known for their negative charge that enables electric currents, their spin property offers untapped potential for advancing data storage technologies.
Traditional methods of controlling electron spin have relied on ferromagnetic materials like iron to align spin polarization with magnetic fields. However, researchers have uncovered an innovative alternative using chiral molecules – structures lacking superimposable mirror images, similar to helices. These molecules have shown remarkable ability to induce spin polarization at levels matching ferromagnetic materials, achieving 60-70 percent efficiency.
The JGU research team, led by Professor Angela Wittmann of the Institute of Physics, has confirmed the chiral-induced spin selectivity (CISS) effect through a groundbreaking hybrid system. Rather than passing current directly through chiral molecules, they created a composite structure combining a thin gold film with chiral molecules on its surface. This arrangement revealed that while current primarily flows through the gold layer, the presence of chiral molecules significantly alters the gold’s properties.
Their investigation focused on the conversion of spin current to charge current, yielding remarkable results. In pure gold films, approximately three percent of spin current converts to charge current, regardless of electron spin orientation. However, the hybrid system demonstrated a dramatic difference: right-handed chiral molecules on the gold surface more efficiently converted spin-up electron currents to charge, while left-handed molecules showed the opposite effect. This relationship between chirality and spin-to-charge conversion efficiency represents a significant breakthrough in spin control.
The research also revealed the vectorial nature of this effect. The spin selectivity only occurs when the electron spin direction aligns either parallel or antiparallel to the chiral molecule’s helix axis. When spin direction deviates from these alignments, the effect disappears, highlighting the precise directional requirements for successful spin manipulation.
This discovery holds profound implications for spintronics – the field of electronics utilizing electron spin. The ability to control electron spin without traditional magnetic materials opens new possibilities for developing more efficient and versatile electronic devices. The confirmation of the CISS effect provides crucial validation for this emerging approach to spin manipulation, potentially leading to innovations in data storage, quantum computing, and other electronic applications.
The research demonstrates how chiral molecules could serve as an elegant alternative to conventional magnetic methods for controlling electron spin. This breakthrough not only advances our understanding of spin dynamics but also suggests new directions for future electronic device development. The precise control offered by chiral molecules, combined with their natural occurrence and diverse forms, makes them particularly promising for next-generation electronic applications.
Professor Wittmann’s team has contributed significantly to validating the spin selectivity effect and establishing the fundamental role of chiral molecules in spin manipulation. Their work provides a solid foundation for future research in this field and brings us closer to practical applications of spin-based electronics. This research represents a crucial step toward harnessing electron spin for advanced technological applications, potentially leading to more efficient and capable electronic devices in the future.
Reference: “Chiral-induced unidirectional spin-to-charge conversion” by Ashish Moharana, Yael Kapon, Fabian Kammerbauer, David Anthofer, Shira Yochelis, Hadar Shema, Elad Gross, Mathias Kläui, Yossi Paltiel and Angela Wittmann, 1 January 2025, Science Advances. DOI: 10.1126/sciadv.ado4285
