Speaking of small things, and I mean extremely small things, scientists have been doing wild experiments to see how electrons flow. Generally, electrons don’t flow like water, with pretty streams and waves and whirlpools and evidence of classic fluid dynamics. The electrical current behavior is more independent, with electrons acting as individuals rather than groups.

Of course, scientists want to see if that is always true, and it turns out that using certain materials and specific conditions, you can make electrons flow like water. In a new paper published in the journal Nature, scientists have observed electrons flowing in vortices – whirlpools – while being squeezed through ultra-clean materials at near absolute zero.

In the experiment, the team used tungsten ditelluride, which has been found to be ultra-clean and exhibits exotic electronic properties under certain conditions. Co-author Leonid Levitov explains: Tungsten ditelluride is one of the new quantum materials where electrons are strongly interacting and behave as quantum waves rather than particles. In addition, the material is very clean, which makes the fluid-like behavior directly accessible.

Just to clarify – clean here describes how the interactions work out, not the actual grime on the material.

Using pure, single crystals of the metal and some electron-beam lithography and plasma etching, they patterned flakes of the tungsten ditelluride with a center channel. On either side of the channel, they etched circular chambers. They repeated the process with gold flakes as well for comparison. Then they ran a current through these patterned samples at 4.5 Kelvin. The electron current was measured using a nanoscale SQUID – a superconducting quantum interference device – which measures magnetic fields to a high degree of precision. And all of this delicate work allowed the team to observe just how the electrons flowed through those channels in the two materials.

The electrons in the gold didn’t reverse direction at all, even in the circular chambers; however, the electrons in the tungsten ditelluride not only reversed directions but actually began to flow around the side chambers. They created small whirlpools before flowing back out into the straight channel. That’s pretty amazing, and as Levitov notes: That is a very striking thing, and it is the same physics as that in ordinary fluids, but happening with electrons on the nanoscale. That’s a clear signature of electrons being in a fluid-like regime.

If you’re asking why in the world would anyone want to do this or even think to do this, the answer is science, first off. But second, engineers are always looking to improve designs and use less power, and this could help them make more efficient devices. Pretty neat stuff.

More Information

MIT press release

“Direct observation of vortices in an electron fluid,” A. Aharon-Steinberg et al., 2022 July 6, Nature