A series of buzzing, bee-like "loop-currents" could explain a phenomenon in a quantum material. Engineers may one day be able to develop new types of devices, such as quantum sensors or the quantum equivalent of computer memory storage devices, based on the findings from the University of Colorado Boulder.
The chemical formula Mn 3 Si 2 Te 6 is used to calculate the quantum material. It's called honeycomb because it's made of two atoms that look like cells in a hive.
Gang Cao and his colleagues at the University of Colorado Boulder were surprised when they synthesised this molecule in their lab in 2020. It didn't allow electric currents to go through it quickly. The honeycomb became less resistant to currents when exposed to magnetic fields. It looked like the rubber had turned into metal.
The new study was both astonishing and puzzling according to the professor who wrote it. The effort to better understand the phenomena led to more surprising discoveries.
They believe they can explain that behavior. Several graduate students at the University of Colorado Boulder published their results in the journal Nature.
The group reported that under certain conditions, the honeycomb is abuzz with internal currents called loop currents. The electrons zip around in loops. Physicists theorize that loop currents could exist in a few materials, such as high-temperature superconductors, but they haven't directly observed them.
The one he and his team stumbled on was a quantum material.
A new quantum state of matter has been found. It's like ice melting into water.
The Colossal is different.
The study has a weird property in physics.
Physicists realized in the 1950s that exposing certain materials to magnets could cause them to switch from insulators to wire-like conductors. This technology is present in many electronic devices where it helps to control and shuttle electric currents.
The honeycomb in question is vastly different from those materials. The electrical properties in the material are more extreme than in any other material.
You need to violate all the conventional conditions to achieve this change.
Ice is melting.
They wanted to find out why.
The idea of loop currents was hit on by them and co-author Itamar Kimchi. The team's theory is that a lot of electrons circulate around inside their honeycombs at all times. In the absence of a magnetic field, the loop currents tend to stay disorderly. Cars are driving through a roundabout in both directions at the same time.
The disorder can cause traffic jams for electrons to travel in the material and make it an insulator.
"Electrons like order," said Cao.
The loop currents will only move in one direction if you pass an electric current into the quantum material. The traffic jams go away. As soon as that happens, electrons can travel through the quantum material like a metal wire.
The internal loop currents are vulnerable to external currents. The loop currents are disrupted when an external electric current goes over a critical threshold.
The switch from one electronic state to another in most materials can be done in a matter of seconds. In his honeycomb, that transformation can take a long time.
The entire structure of the honeycomb is thought to be morphing with the bonds between atoms breaking. It takes a long time for that sort of reordering to happen.
The work provides a new way of thinking about quantum technologies. You will probably not see this honeycomb in any new electronic devices. The switch behavior only happens at cold temperatures. He and his colleagues are looking for materials that will do the same thing.
If we want to use this in future devices, we need to have materials that show the same behavior at room temperature.
That kind of invention could get a lot of attention.
More information: Gang Cao, Control of chiral orbital currents in a colossal magnetoresistance material, Nature (2022). DOI: 10.1038/s41586-022-05262-3. www.nature.com/articles/s41586-022-05262-3 Journal information: Nature
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