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Engineers advance quantum electronics

Duke engineers have paved a path toward the next generation of quantum electronic devices.

Stefano Curtarolo, professor of mechanical engineering and materials science and director of the Center for Materials Genomics, and his team of researchers have created a database of more than 2,000 compounds that can be combined to create quantum electronic devices—devices smaller than conventional wires that can create electricity efficiently. Relying on a specified formula, the database is able to scan materials, find their particular properties, thereby determining the different tasks they can perform.

A major asset of the database is its ability to find topological insulators—man-made crystals that conduct an electrical current on the surface of the compounds. TIs have the potential to change nanoelectronics because they are ideal candidates for making quantum electronic devices, Curtarolo said.

“When you’re at the forefront of research, you don’t know what problems you are going to find tomorrow,” he said. “It’s like climbing a mountain that’s never been climbed before—we need to try different directions and hope one direction will not bring us down.”

Using the database, Curtarolo and his team were able to find a new class of TIs. He noted that many scientists thought such compounds could not be used for creating TIs given their reliance on a limited group of previously tested compounds. The database, however, allows for an unbiased analysis of potential compounds.

Currently, when making materials that can conduct electricity, certain supplies are needed, Curtarolo noted. For example, the process to make an inductor—an electrical component that stores energy—requires a wire. With TIs, the direction the crystal grows in determines how it will conduct electricity, so supplies typically used to make electrical components are not needed.

“You can make a slow substrate, like silicon, and then grow [the crystals] in different directions, and naturally [they] will be different devices,” he said. “These materials are very powerful, but the biggest problem is that too few are known—searching for them is the biggest issue.”

Kesong Yang, a postdoctoral fellow in Curtarolo’s laboratory and first author of the paper, noted that the database could be used for more than just finding TIs.

“This database is very useful not only for TIs but also for finding other materials, like other compounds that can be used for properties,” he said.

Curtarolo added that one use is finding thermoelectric materials, which can be used to convert heat into energy.

Despite the discovery of many TIs, Curtarolo and his team have not yet made a quantum electronic device.

“If you want to make a big crystal, it can take a year,” he said. “We cannot wait for the test because if someone else comes out with the material and a patent, we lose a lot of money.”

It will take some time to determine whether the TIs listed in the database are better than what is currently listed, in terms of manufacturing and cost, he noted.

Even with these advancements, using the database has not always been easy, said Shidong Wang, postdoctoral associate on Curtarolo’s team.

“You have to run the correct programs and think about how effective the execution of the database will be so you can do things in a fast way,” he said. “It takes one month to finish each project and it’s a lot of energy.”

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