IIT-Madras scientist part of team demonstrating electrically driven molecular rotation

CHENNAI: An IIT-Madras scientist is part of an international research team that has demonstrated how electrical current can drive the rotation of a single molecule, while the rotation itself can enhance electrical conduction by up to 100-fold, offering new insights into molecular-scale electronic systems.

The findings, published in Nature, establish a feedback mechanism between molecular motion and electrical transport at the atomic scale, with potential applications in future nanoscale technologies.

Assistant Professor Anil Kumar Singh, Department of Physics, IIT-M, is a corresponding author and the principal experimental contributor to the study, which involved researchers from India, Israel, Germany, Denmark and China. The team investigated a molecular rotor made of helicene, a spiral-shaped molecule suspended between two gold electrodes.

When voltage was applied, the molecule moved through a cyclic sequence of configurations. Reversing the voltage polarity reversed the sequence, demonstrating electrical control over the direction of molecular motion.

In all 122 cases where transition directions could be determined, the researchers observed the same cyclic sequence. They also recorded a sharp increase in current as the molecule shifted from stepwise movement to continuous rotation, passing through configurations that allowed electrons to flow more readily.

“An exciting aspect of this work is that molecular motion is not merely a consequence of electrical transport; it can also facilitate the passage of electrons through the molecule,” Singh said.

Researchers said that the findings could inform the development of molecular-scale switches and current-modulating components. However, Singh cautioned, “The study is a proof-of-principle demonstration, not a technology ready for practical use. The experiments were conducted at 4.2 kelvin, about minus 269 degrees Celsius. More research is needed to establish reliable operation under practical conditions.”