After years of searching, physicists have discovered that electrons are trapped in fluid-like whirlpools

(ORDO NEWS) — For the first time, physicists have witnessed an incredibly exciting phenomenon: electrons form whirlpools, like a liquid.

Scientists have long predicted this behavior, but have never observed it before. And it could be the key to developing more efficient and faster next-generation electronics.

“Electronic vortices are theoretically expected, but there was no direct evidence, and seeing is believing,” says one of the authors of the new study, physicist Leonid Levitov from the Massachusetts Institute of Technology.

“Now we’ve seen it, and it’s a clear sign that we’re in a new regime where the electrons behave like a liquid, not like individual particles.”

While electrons flowing in a vortex may not sound like much of a revolution, it is very important because when moving as a fluid, more energy is delivered to the end point rather than being lost along the way when the electrons collide with things like impurities in the material or vibrations. in atoms.

“We know that when the electrons go into a liquid state, [energy] dissipation is reduced, and this is of interest in the development of low-power electronics,” says Levitov. “This new observation is another step in that direction.”

The work was a collaborative experiment between the Massachusetts Institute of Technology, the Weizmann Institute of Science in Israel, and the University of Colorado Denver.

Of course, we already know that electrons can bounce off each other and flow without resistance in superconductors, but this is the result of the formation of something known as “Cooper pairs” and is not a true example of the collective flow of electrons as a fluid.

Let’s take water for example. Water molecules are separate particles, but they move as a whole in accordance with the principles of hydrodynamics, carrying each other over the surface, creating currents and whirlpools.

Electric current, in fact, should be able to do the same, but any collective behavior of electrons is usually canceled out by impurities and vibrations in ordinary metals and even semiconductors. These “distractions” knock the electrons astray and prevent them from exhibiting fluid-like behavior.

It has long been predicted that in special materials at a temperature close to zero, these interferences should disappear, allowing electrons to move like a liquid… but the problem was that until now no one could prove that this is exactly the case.

The fluid has two fundamental features: linear flow, when individual particles flow in parallel as a whole, and the formation of vortices and eddies.

The first was noticed by Levitov and his colleagues at the University of Manchester in 2017 using graphene as an example. In thin sheets of carbon, Levitov and his team showed that electric current could flow through a pinch point as a liquid rather than as grains of sand.

But no one saw the second feature. “The most striking and ubiquitous feature of the flow of ordinary fluids – the formation of vortices and turbulence – has not yet been observed in e-fluids, despite numerous theoretical predictions,” the researchers write.

To find out, the team took pure single crystals of an ultrapure material known as tungsten ditelluride (WTe2) and cut them into flakes one atom thick.

They then etched the design into a central channel with circular chambers on either side, creating a “maze” for the electrical current to flow through. They etched the same pattern onto flakes of gold, which does not have the same ultrapure properties as tungsten ditelluride and therefore acted as a control.

After years of searching physicists have discovered that electrons are trapped in fluid like whirlpools 2
The diagram on the left shows how electrons flowed in the gold (Au) flake experiment. The figure on the right shows a simulation of how they think the fluid-like electrons should behave

After cooling the material to about -269 degrees Celsius (4.5 Kelvin or -451.57 Fahrenheit), they ran an electric current through it and measured the flow at certain points in the material to determine how the electrons were flowing.

In the gold flakes, the electrons passed through the labyrinth without changing direction, even as the current passed through each side chamber, before returning to the main current.

In tungsten ditelluride, by contrast, the electrons flowed through the channel, then swirled in each side chamber, creating whirlpools, and then flowed back into the main channel – as liquids should.

“We observed a change in flow direction in chambers where the direction of flow was reversed compared to the direction of flow in the central lane,” says Levitov.

“It’s a very striking thing, and it’s the same physics as in ordinary liquids, but happening to electrons at the nanoscale. It’s a clear indication that the electrons are in a liquid-like regime.”

After years of searching physicists have discovered that electrons are trapped in fluid like whirlpools 3
The column on the left shows how the electrons passed through tungsten ditelluride (WTe2) compared to the hydrodynamic simulation in the left column

Of course, this experiment was conducted at ultra-cold temperatures with a specialized material – not something that will soon be happening in your home gadgets. There were also restrictions on the size of the cameras and the middle channel.

But this is “the first direct visualization of vortices in an electric current,” as the press release explains. Not only does this confirm that electrons can behave like a liquid, but it could also help engineers better understand how to use this potential in their devices.

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