Quantum computers have to be kept cold to function—very cold. These machines generally run at "just a few degrees above absolute zero," says Yoseob Yoon, assistant professor of mechanical and industrial engineering at Northeastern University. "It's colder than outer space."
Yoon's research focuses on "controlling material properties using lasers," he says.
In other words, he shoots light at atomically thin materials to get them moving in novel ways.
One of his principal materials is something called graphene, a two-dimensional surface whose discoverers received the Nobel Prize in Physics in 2010, Yoon says.
Yoon produces graphene through what he calls the Scotch Tape method. "I have a few millimeter-wide and -thick bulk materials of, for example, graphite," he says, the same carbon derivative found in pencils. "I basically use Scotch Tape—literally—and then I peel off" ultra-thin samples from the bulk material.
These samples are the thickness of a single atom, "without any roughness," he says.
There already existed a field studying "thermal transport using thin metallic films," Yoon says. By firing lasers at very thin metals, researchers can induce controlled oscillations like acoustic waves in drums.
However, "this has been limited to gigahertz regimes, because these metals are very heavy, and they cannot be controlled down to monolayer thickness.
"And then there is another field, basically a 2D-material field," he continues. "They exfoliate these atomically thin layers."
Yoon's breakthrough came in combining these two fields. By aligning atomically thin structures with the study of laser-based thermal transport, "there's a new regime that we couldn't achieve before."
Now, in a paper published in Nature, Yoon and his collaborators have identified novel van der Waals heterostructures (created by combining layers of these atomically thin materials, including graphene and other varieties) that allow control at terahertz frequencies.
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