It began as a lab accident. When the researchers were putting graphene on the surface of a platinum crystal, the single layer of carbon atoms didn’t align perfectly, creating a strain in the structure.
Nanobubbles formed on the surface. And this caused the electrons to act like they were in a large pseudo-magnetic field.
This is a big deal because the way electrons move is fundamental to electronic devices. Manipulating how electrons move can change graphene’s conductivity and its optical or microwave properties. That’s why controlling the strain of the material is a powerful tool to have if you want to use graphene as a replacement for silicon in electronic devices.
As you see in the picture to the right, the nanobubbles created an uneven energy distribution. So, this makes the electrons behave in a peculiar way.
It’s a “pseudo” magnetic field because it doesn’t rely on a magnet to move electrons. (The Large Hadron Collider needs magnets).
The University of California, Berkeley researchers discovered that when they put a strain on graphene, the electrons in a single sheet of carbon atoms behaved as if they were in a magnetic field as strong as 300 tesla (a measure of magnetic fields, not the car).
In theory, this isn’t new. Back in 1997, researchers predicted that they could create a pseudo-magnetic field. But this was for carbon nanotubes (the Fruit Roll-Ups of graphene, not the flat version).
Now, for the first time, the magnetic field affect was observed on a flat sheet. When the researchers created a layer of graphene on top of platinum, the nanobubbles were stretched until they became a pyramid structure that had unique magnetic properties.
Scientists have studied magnetic fields before, but couldn’t really make them last for more than a few thousandths of a second. The record holder for electromagnetism was measured at 85 tesla.
The Berkeley researchers broke the record.
“We have shown experimentally that when graphene is stretched to form nanobubbles on a platinum substrate, electrons behave as if they were subject to magnetic fields in excess of 300 tesla, even though no magnetic field has actually been applied,” Berkeley physicist Michael Crommie said in a statement.
“When you crank up a magnetic field you start seeing very interesting behavior because the electrons spin in tiny circles,” he added. “This effect gives us a new way to induce this behavior, even in the absence of an actual magnetic field.”
Graphene is strong, extremely conductive, flexible, and transparent — and clearly becoming a preferred alternative to silicon.
Photo: Crommie lab at UC Berkeley
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