Physicists have witnessed for the first time something incredibly exciting: electrons forming vortices just like those seen in liquids. Scientists have long predicted this behavior, but never seen it before, and it may be the key to developing next-generation electronics with greater efficiency and faster performance.
Theories predict the movement of electrons in vortices
The physicist Leonid Levitov from Massachusetts Institute of Technology And one of the researchers in the new study: “The electron vortices are theoretically expected, but there is no direct evidence, but seeing them is the best evidence, as we have seen that now, and it is clear evidence that electrons behave as a liquid in this new system, and not as single particles.”
While electrons flowing in a vortex may not seem like a new thing, it is very important because flowing like a liquid leads to more energy being delivered to the end point, rather than losing it along the way as electrons scramble around things like impurities in materials or vibrations in atoms.
Electrons move like fluids
And he said Levitov: “We know that when electrons move like a liquid, the dissipation decreases [الطاقة]This is important in trying to design low-power electronics. This new monitoring is another step in that direction.”
Of course, we already know that electrons can bounce off one another and flow without resistance in superconductors, but this is the result of the formation of something known as “Cooper pairs”, and not a true example of electron flow as a whole as the flow of a liquid.
Take water, for example. Water molecules are individual molecules, but they travel together according to the principles of fluid dynamics, carrying each other across the surface, forming currents and eddies as they travel.
An electric current should be able to do essentially the same thing, but usually bypass any collective behavior of electrons due to impurities and vibrations in ordinary metals and even semiconductors. These “dispersants” cause electrons to fly around as they travel and prevent them from exhibiting fluid-like behavior.
Using graphene to prove the flow of electrons as a liquid
Scientists had long expected that these interferences should disappear into special materials at temperatures close to zero to allow electrons to move like liquids… But the problem was that no one was actually able to prove this, until today.
There are two basic characteristics of a fluid: linear flow, in which all the separate particles flow in parallel in one image, and the formation of vortices and circles.
Levitov and his colleagues first observed the feature at the University of Manchester in 2017 using graphene, a plate made up of a single layer of carbon atoms, and using it between Levitov and his team that an electric current can flow through a pressure point as a liquid flows, not as grains of sand cascade.
As for the second feature, which no one had seen before, the researchers wrote: “The most striking and prevalent feature in the flow of uniform fluids is the formation of vortices and turbulence, but it has not yet been observed in electron fluids despite many theories that have predicted it.”
To find out, the team took single pure crystals of an ultra-pure material known as tungsten dichloride, and cut it into thin slices, about an atom thick.
They then carved a pattern in a central channel with a circular chamber on either side, creating a “labyrinth” for an electric current to pass through. They also engraved the same pattern on gold foil that did not have the same ultra-clean properties as tungsten dichloride, thus acting as a controlling element.
The above diagram from the left shows how electrons flow in the experiment in gold (Au) foil. The image on the right shows a simulation of how scientists predict fluid-like behavior of electrons.
After the material had cooled to about -269 degrees Celsius, the team ran an electric current through it and measured the flow at specific points throughout the material, in order to map how the electrons flowed.
It was observed that the electrons in the gold foil passed through the maze without changing direction, even as the current passed through each side chamber before returning to the main stream.
In contrast, electrons within tungsten dichloride flow through the channel and then spin into each side chamber, forming vortices, before flowing back into the main channel – as you’d expect a liquid to do.
“We observed a change in the direction of flow in the chambers, where the flow reversed direction compared to the direction in the central strip,” Levitov said.
He added, “This is quite amazing, and it is similar to the physics of ordinary fluids, but it happens with electrons at the nano level. It is clear evidence that electrons exist in a system similar to a fluid system.”
The left column in the above graphic shows how electrons flow through tungsten dichloride compared to the hydrodynamic simulation in the left column.
First visualization of electron vortices
Of course, the experiment was conducted at very cold temperatures with a material intended for this purpose, as this will not happen in household appliances for the foreseeable future. There were also restrictions on the size of the rooms and the middle channel.
But this is “the first direct visualization of vortices in an electric current,” the press release explains. Not only is this assertion that electrons can behave like liquids, but this advance may also help engineers better understand how to harness this potential in their devices.
nature