How to cook up a new topological insulator

By Hamish Johnston
First predicted in 2005 and confirmed in the lab in 2007, topological insulators (TI) are perhaps the hottest material in condensed-matter physics these days. As well as constituting a new phase of quantum matter that should keep physicists busy for some time, the material has recently been shown to harbour quasiparticles resembling Majorana fermions. First predicted by the Italian physicist Ettore Majorana in 1937, such particles could be used to store and transmit quantum information without being perturbed by the outside world. As such, they could find use in the quantum computers of the future.

It’s not surprising that scientists worldwide are working hard to discover and study new variants of TIs. However, researchers at Duke University in the US believe that, until now, discoveries have been based on trial and error.

To encourage a more systematic approach, Stefano Curtarolo (right) and colleagues have created a “master ingredient list” that describes the properties of more than 2000 compounds that could be combined to make TIs. The clever bit of the work is a mathematical formulation that helps database users search for potential TIs that are predicted to have certain desirable properties.

The system is based on Duke’s Materials Genome Repository, which has already been used to develop both scintillating and thermoelectric materials.

According to Curtarolo, the system gives practical advice about the expected properties of a candidate material – for example, whether it will be extremely fragile or robust.

Commenting on the fragile materials, Curtarolo says “We can rule those combinations out because what good is a new type of crystal if it would be too difficult to grow, or if grown, would not likely survive?”

The research is also described in a paper published in Nature Nanotechnology.