Scientists with the University of Chicago and Shanxi University announced that they have created a way to use lasers to “simulate” a material that physicists have been drooling over for its potential technological applications for years.
This new method could be used to better understand how materials work—known as a twisted two-layer lattice—and could perhaps point the way to new electronics or quantum technologies.
The work was published in Natural.
Twist on Tradition
Four years ago, scientists at MIT discovered a surprise: Thin sheets of ordinary carbon atoms can become superconducting if you rotate the sheets as you stack them.
Superconductors are a rare type of material that can conduct electricity perfectly, without any loss. Scientists and engineers can imagine all kinds of uses for superconductors—they’re already the basis of MRI—but they have significant limitations, including having to be cooled below zero to work. Scientists hope that if they can fully understand the principles of physics at play, they can design new superconductors that open up all kinds of technological possibilities.
“Every time someone discovers a new class of superconductors, the world of physics sits up and takes notice,said Cheng Chin, professor of physics at the University of Chicago and one of the authors of the new study. “But this one is really interesting because it’s based on a simple and common material like graphene.”
Graphene is the simplest material: it’s a thin lattice of carbon atoms. Scientists jumped to explore the possible applications, sparking a flood of research into a new field called twisted electronics, or “twistronics”.
But despite how simple graphene is in some ways, it’s been a bit difficult to study how graphene can become a superconductor when stacked in these twisted sheets. For example, scientists want to rotate the sheets a little at a time and see what happens to the properties each time; but graphene sheets tend to stick to each other and will tear if moved.
Chin’s lab and the Shanxi group had previously devised a way to replicate complex quantum materials using cooled atoms and lasers to make them easier to study—so they thought they could do the same for a twisted two-layer system.
Working with researchers at Shanxi University, the team devised an innovative way to “simulate” this bent lattice.
They took atoms of an element called rubidium, chilled them, and used lasers to arrange them into two lattices, one on top of the other. Then, to help the two gratings interact with each other, the scientists used microwaves.
This combination works. The material displays “superfluidity”—a property similar to superconductivity, in that particles can flow through it without being slowed down by friction. Using the system, the researchers observed a new form of superfluid inside the atom, thanks to the ability to adjust the twisting angle of the two lattices.
By changing the strength of the microwaves, scientists found that they could control how strongly the two lattices interact. Meanwhile, they can easily rotate two grids with a laser.
“This makes it a very flexible system,” he said. “For example, some people want to explore more than two layers to three or even four. It would be easy to do with our setup.”
By using this new setting to explore this twisted two-layer lattice, scientists hope to enable breakthroughs for new materials for electronics or ways to control information in quantum technology.
The co-authors of the study also include researchers from Zhejiang Normal University and Hefei National Laboratory of China.