Water is a mysterious substance. Understanding its behavior on an atomic scale remains challenging for experimentalists as the light hydrogen and oxygen atoms are challenging to see with conventional experimental probes. This is particularly evident when trying to observe the microscopic movement of individual water molecules, which occurs on a picosecond timescale.
Scientists now present an experimental and computational study of the nanoscale-nanosecond motion of water at the surface of a topological insulator.
Scientists from the Exotic Surfaces group at TU Graz’s Institute of Experimental Physics joined forces with counterparts from the Cavendish Laboratory at the University of Cambridge, the University of Surrey, and Aarhus University.
In collaboration, they developed significant advances, performing research into the water behavior of the topological insulator bismuth telluride.
As scientists noted, “This compound could be used to build quantum computers. Water vapor would then be one of the environmental factors to which applications based on bismuth telluride may be exposed during operation.”
During the study, scientists combined a new technique called helium spin echo spectroscopy and theoretical calculations. Helium spin-echo spectroscopy uses low-energy helium atoms, which permits the movement of isolated water molecules to be seen without disturbance.
Scientists observed that the water molecules behave entirely differently on bismuth telluride compared to those on conventional metals. They report clear evidence for repulsive interactions between water molecules, which is contrary to the expectation that attractive interactions dominate the behavior and aggregation of water on surfaces.
Bismuth telluride appears to be insensitive to water, which is an advantage for applications under typical environmental conditions. Plans are in place for further experiments on similarly structured surfaces, intended to clarify whether the movement of water molecules is attributable to specific features of the surface in question.
Journal Reference
- Tamtögl, A., Sacchi, M., Avidor, N. et al. Nanoscopic diffusion of water on a topological insulator. Nature Communications 11, 278 (2020). DOI: 10.1038/s41467-019-14064-7