Stanene (from the Latin stannum, meaning tin, which also gives the element its chemical symbol, Sn) is the latest cousin of graphene, the honeycomb lattice of carbon atoms that has spurred thousands of studies into related 2D materials.
Two years ago, physicists have predicted that tin should be able to form a mesh just one atom thick, and might even stand out from the other graphene-inspired materials by possessing a number of exotic electronic properties, such as the capacity to conduct electricity without losing any of it to heat.
In 2013, the Stanford University physicist Shou-Cheng Zhang, who’s also a co-author on the present paper, predicted that, if it were ever to be made, stanene would be an example of a topological insulator, which allow charge carriers (such as electrons) to travel only along their edges, but not the centre, thereby preventing any energy loss that would be unavoidable in other materials. This unique property would make stanene ideal for transporting current in electric circuits.
Now, this promising new material has been made, and yet Zhang and his colleagues from four universities in China are still uncertain whether it’s really all it’s been cracked up to be – so far, neither of the teams had succeeded in confirming that it is, as a matter of fact, a topological insulator.
The material has been developed by vaporising tin in a vacuum and allowing the atoms to settle down onto a supporting surface crafted from bismuth telluride (a semiconductor that combines bismuth and tellurium). Although this surface allows for the formation of stanene’s two-dimensional crystals, it also interacts with them, creating the wrong conditions for a topological insulator.
Exotic electronic properties aside, there have even been doubts as to whether the researchers really made the material in the first place. Currently, Zhang’s team has only been able to see the upper ridge of atoms with their scanning tunnelling microscope, which leaves it uncertain if the tin lattice really forms the predicted buckled honeycomb structure, with alternate atoms folding upwards to form corrugated ridges.
Zhang, however, is confident about his team’s discovery, partly because the distance between ridges matches predictions.
“I think the work is a significant breakthrough that once again expands the 2D-material universe,” said Yuanbo Zhang, a physicist at Fudan University in Shanghai, China, who was not involved in the study. “It’ll be exciting to see how the material lives up to its expectations.”
The process of making the new material is detailed in a paper published on August 3 in Nature Materials.