What the research is about
Many of the materials inside smartphones and computers perform specific jobs, such as carrying electrical current or storing information. Once made, however, their properties are generally fixed. But what if a material’s properties could be switched on demand-even while a device is operating? Such a capability could allow a single material to perform multiple functions, opening the way to new electronic devices.
One promising approach is intercalation, a technique that inserts and removes ions or molecules between the layers of a material. Intercalation is already used in lithium-ion batteries, where lithium ions move in and out of electrode materials during charging and discharging. Because this process is reversible, batteries can be recharged repeatedly. Researchers have also explored intercalation as a way to change the electrical and magnetic properties of materials.
More recently, scientists have discovered that introducing chiral molecules-molecules that exist in two mirror-image forms, like right and left hands-into materials can create a unique property in which electrons flow through the material more or less easily depending on their spin direction. However, once these chiral molecules were incorporated, the material’s chirality became fixed, making it impossible to switch the material’s properties on demand while a device was in operation.
Why this matters
How can a material’s chiral state be turned on when needed-and switched off again? A research team led by Professor Kouji Taniguchi at Institute of Science Tokyo (Science Tokyo) focused on chiral molecules small enough to move into and out of a material.
The researchers developed a method to electrochemically insert and remove these tiny chiral molecules from a layered semiconductor called molybdenum disulfide (MoS₂). Using this approach, they demonstrated for the first time that a material could be repeatedly switched between chiral and non-chiral states using only electricity.
The team confirmed that the molecules were reversibly inserted and removed using multiple analytical techniques, including X-ray diffraction and Raman spectroscopy. They also demonstrated that the material’s ability to preferentially conduct electrons according to their spin direction could be switched on and off together with its chirality. The material achieved a spin selectivity of approximately 99%, indicating nearly perfect spin selectivity.
What’s next
This study demonstrates that the chirality of a material can be reversibly controlled using electricity. The technology could contribute to the development of spintronics, a next-generation field of electronics that makes use of electron spin as well as charge.
In the future, it could lead to electronic devices that control electron transport without magnets, as well as faster and more energy-efficient information-processing technologies.
More broadly, this work challenges the conventional idea that a material’s properties are fixed once it has been made. Instead, it represents an important step toward designing materials whose properties can be switched whenever needed.
Comment from the researcher
Researchers have previously succeeded in creating chiral materials by inserting chiral molecules into layered materials, but their chiral state could not be reversibly switched without damaging the material. Inspired by the operating principle of lithium-ion battery, we have now shown that electricity can be used to reversibly control not only a material’s electrical properties but also chirality-a property arising from the structure of the material. We hope this achievement will contribute to the realization of next-generation devices, including spintronic technologies.
(Kouji Taniguchi, Professor, School of Science, Institute of Science Tokyo)
Dive deeper
Related research by Professor Koji Taniguchi
Explore more research in Science for All
Science for All showcases cutting-edge research at Science Tokyo and highlights the ideas, people, and possibilities shaping the future.
