The authors suggest the magnetism, called orbital ferromagnetism, could prove useful for certain applications, such as quantum computing. The group describes their finding in the July 25 issue of the journal Science.
"We were not aiming for magnetism. We found what may be the most exciting thing in my career to date through partially targeted and partially accidental exploration," said study leader David Goldhaber-Gordon, a professor of physics at Stanford's School of Humanities and Sciences. "Our discovery shows that the most interesting things turn out to be surprises sometimes."
Stanford - Researchers - Discovery - Finding - Shockwaves
The Stanford researchers inadvertently made their discovery while trying to reproduce a finding that was sending shockwaves through the physics community. In early 2018, Pablo Jarillo-Herrero's group at MIT announced that they had coaxed a stack of two subtly misaligned sheets of carbon atoms -- twisted bilayer graphene -- to conduct electricity without resistance, a property known as superconductivity.
The discovery was a stunning confirmation of a nearly decade-old prediction that graphene sheets rotated to a very particular angle should exhibit interesting phenomena.
Graphene - Forms - Superlattice - Interference - Moiré
When stacked and twisted, graphene forms a superlattice with a repeating interference, or moiré, pattern. "It's like when you play two musical tones that are slightly different frequencies," Goldhaber-Gordon said. "You'll get a beat between the two that's related to the difference between their frequencies. That's similar to what you get if you stack two lattices atop each other and twist them so they're not perfectly aligned."
Physicists theorized that the particular superlattice formed when graphene is rotated to 1.1 degrees causes the normally varied energy states of electrons in the material to collapse, creating what they call a flat band where the speed at which electrons move drops to nearly zero. Thus slowed, the motions of any one electron becomes highly dependent on those of others in its vicinity. These interactions lie...
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