After years of research, physicists observe electrons flowing in fluid-like vortices

For the first time, physicists have witnessed something incredibly exciting: electrons form vortices just like liquids.

This behavior has long been predicted by scientists, but has not been observed before. And it could be the key to developing more efficient and faster next-generation electronics.

“Electronic vortices are theoretically expected, but there is no direct evidence, and vision is a believer,” says physicist Leonid Levitov of the Massachusetts Institute of Technology, one of the researchers.

“We’ve seen it now, and it’s clear evidence of being in this new system, where electrons behave like a liquid, not as individual particles.”

While electrons flowing in a vortex may not appear to be groundbreaking, this is a major problem because flowing like a liquid leads to more energy being delivered to the end point, rather than losing it on the way as the electrons scramble around things like impurities in materials or vibrations in atoms. .

“We know when electrons are moving in a liquid state, [energy] The dissipation goes down, which is important in trying to design low-power electronics,” Levitov says. This new observation is another step in that direction. “

The work was a joint experiment between the Massachusetts Institute of Technology, the Weizmann Institute of Science in Israel and the University of Colorado in 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’, not a true example of electrons flowing collectively like liquids.

Take water for example. Water molecules are individual molecules, but they travel as one 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 any collective behavior of electrons is usually overridden by impurities and vibrations in ordinary metals and even semiconductors. These “scatterers” knock electrons out as they travel and prevent them from exhibiting fluid-like behaviour.

It has long been predicted that within special materials at temperatures close to zero, these interferences should disappear to allow electrons to move around like liquids…but the problem hasn’t been really proven, until now.

There are two basic characteristics of a fluid: linear flow, in which all separate particles flow in parallel as one; Swirls and vortices are formed.

The first was observed by Levitov and colleagues at the University of Manchester in 2017 using graphene. In atom-thin carbon sheets, Levitov and his team showed that an electric current can flow through a pressure point like a liquid, not like grains of sand.

But no one saw the second advantage. “The most striking and most prevalent feature of uniform fluid flow, the formation of vortices and turbulence, has not yet been observed in electron fluids despite several theoretical predictions,” the researchers wrote.

To find out, the team took pure single crystals of an ultra-clean material known as tungsten dichloride (WTe).2) and cut into thin strips of one corn.

Then they drilled a pattern in a central channel with a circular chamber on either side, creating a “maze” for an electric current to pass through. They etched the same pattern onto gold foil, which does not have the same ultra-clean properties as tungsten diethyluride and thus served as a control.

(Aaron Steinberg et al., temper nature2022)

Above: The graph on the left shows how electrons flow in the experiment in gold (Au) foil. The image on the right shows a simulation of how they predict the behavior of electrons, similar to liquids.

After cooling the material to about -269 degrees Celsius (4.5 Kelvin or -451.57 Fahrenheit) they run an electric current through it and measure the flow at specific points throughout the material, to map how the electrons flow.

In gold foil, electrons flow through the maze without changing direction, even as current passes through each side chamber before returning to the main stream.

In contrast, within the tungsten ditelluride, the electrons 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 direction of flow reversed compared to that in the central strip,” says Levitov.

“This is something very amazing, and it’s the same physics found in ordinary liquids, but it happens with electrons at the nanoscale. This is clear evidence that electrons exist in a fluid-like system.”

simulation(Aaron Steinberg et al., temper nature2022)

Above: The column on the left shows how electrons flow through tungsten ditelluride (WTe).2) compared to the hydrodynamic simulation at left vertical.

Of course, this experiment was conducted in very cold temperatures using specialized material – this is not going to happen in your home appliances anytime soon. There were also restrictions on the size of the rooms and the middle channel.

But this is “the first direct visualization of vortex vortices in an electric current” as the press release explains. This is not only a confirmation that electrons Can Acting as a fluid, the advance could also help engineers better understand how to harness this potential in their devices.

The search was published in temper nature.

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