Though they are discrete particles, water molecules flow collectively as liquids, producing streams, waves, whirlpools, and other classic fluid phenomena. | |
Not so with electricity. While an electric current is also a construct of distinct particles — in this case, electrons — the particles are so small that any collective behavior among them is drowned out by larger influences as electrons pass through ordinary metals. But, in certain materials and under specific conditions, such effects fade away, and electrons can directly influence each other. In these instances, electrons can flow collectively like a fluid. | |
Now, physicists at MIT and the Weizmann Institute of Science have observed electrons flowing in vortices, or whirlpools — a hallmark of fluid flow that theorists predicted electrons should exhibit, but that has never been seen until now. | |
“Electron vortices are expected in theory, but there’s been no direct proof, and seeing is believing,” says Leonid Levitov, professor of physics at MIT. “Now we’ve seen it, and it’s a clear signature of being in this new regime, where electrons behave as a fluid, not as individual particles.” |
The observations, reported in the journal Nature (“Direct observation of vortices in an electron fluid”), could inform the design of more efficient electronics. | |
“We know when electrons go in a fluid state, [energy] dissipation drops, and that’s of interest in trying to design low-power electronics,” Levitov says. “This new observation is another step in that direction.” | |
Levitov is a co-author of the new paper, along with Eli Zeldov and others at the Weizmann Institute for Science in Israel and the University of Colorado at Denver. | |
A collective squeeze |
|
When electricity runs through most ordinary metals and semiconductors, the momenta and trajectories of electrons in the current are influenced by impurities in the material and vibrations among the material’s atoms. These processes dominate electron behavior in ordinary materials. | |
But theorists have predicted that in the absence of such ordinary, classical processes, quantum effects should take over. Namely, electrons should pick up on each other’s delicate quantum behavior and move collectively, as a viscous, honey-like electron fluid. This liquid-like behavior should emerge in ultraclean materials and at near-zero temperatures. | |
In 2017, Levitov and colleagues at the University of Manchester reported signatures of such fluid-like electron behavior in graphene, an atom-thin sheet of carbon onto which they etched a thin channel with several pinch points. They observed that a current sent through the channel could flow through the constrictions with little resistance. This suggested that the electrons in the current were able to squeeze through the pinch points collectively, much like a fluid, rather than clogging, like individual grains of sand. | |
This first indication prompted Levitov to explore other electron fluid phenomena. In the new study, he and colleagues at the Weizmann Institute for Science looked to visualize electron vortices. As they write in their paper, “the most striking and ubiquitous feature in the flow of regular fluids, the formation of vortices and turbulence, has not yet been observed in electron fluids despite numerous theoretical predictions.” | |
Channeling flow |
|
To visualize electron vortices, the team looked to tungsten ditelluride (WTe2), an ultraclean metallic compound that has been found to exhibit exotic electronic properties when isolated in single-atom-thin, two-dimensional form. | |
“Tungsten ditelluride is one of the new quantum materials where electrons are strongly interacting and behave as quantum waves rather than particles,” Levitov says. “In addition, the material is very clean, which makes the fluid-like behavior directly accessible.” | |
The researchers synthesized pure single crystals of tungsten ditelluride, and exfoliated thin flakes of the material. They then used e-beam lithography and plasma etching techniques to pattern each flake into a center channel connected to a circular chamber on either side. They etched the same pattern into thin flakes of gold — a standard metal with ordinary, classical electronic properties. | |
They then ran a current through each patterned sample at ultralow temperatures of 4.5 kelvins (about -450 degrees Fahrenheit) and measured the current flow at specific points throughout each sample, using a nanoscale scanning superconducting quantum interference device (SQUID) on a tip. This device was developed in Zeldov’s lab and measures magnetic fields with extremely high precision. Using the device to scan each sample, the team was able to observe in detail how electrons flowed through the patterned channels in each material. | |
The researchers observed that electrons flowing through patterned channels in gold flakes did so without reversing direction, even when some of the current passed through each side chamber before joining back up with the main current. In contrast, electrons flowing through tungsten ditelluride flowed through the channel and swirled into each side chamber, much as water would do when emptying into a bowl. The electrons created small whirlpools in each chamber before flowing back out into the main channel. | |
“We observed a change in the flow direction in the chambers, where the flow direction reversed the direction as compared to that in the central strip,” Levitov says. “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.” | |
The group’s observations are the first direct visualization of swirling vortices in an electric current. The findings represent an experimental confirmation of a fundamental property in electron behavior. They may also offer clues to how engineers might design low-power devices that conduct electricity in a more fluid, less resistive manner. |
News
Ethics in Nanomedicine: Key Issues and Principles
Nanomedicine, a branch of nanotechnology, is revolutionizing healthcare by enabling the manipulation of materials at the nanoscale to diagnose, treat, and prevent diseases. Unlike traditional treatments, nanoparticles (NPs) are highly precise in targeting diseased [...]
A call for robust H5N1 influenza preparedness and response
As the global threat of H5N1 influenza looms with outbreaks across species and continents including the U.S., three international vaccine and public health experts say it is time to fully resource and support a [...]
Mucosal COVID-19 boosters outperform mRNA shots in preventing upper airway infections
In a recent study published in Nature Immunology, a team of researchers from the United States used non-human primate models to compare the protection conferred by an intramuscular booster dose of the bivalent messenger ribonucleic acid [...]
How Space Travel Really Changes Astronauts – From the Inside Out
International team reveals previously unknown effects on physiology that could shape the future of long-duration space missions. Researchers have discovered significant changes in the gut microbiome due to spaceflight, which affects host physiology and [...]
Breakthrough in blood stem cell development offers hope for leukemia and bone marrow failure
Melbourne researchers have made a world first breakthrough into creating blood stem cells that closely resemble those in the human body. And the discovery could soon lead to personalized treatments for children with leukemia [...]
Scientists Develop Game-Changing Needle-Free COVID-19 Intranasal Vaccine
A new mucosal COVID-19 vaccine poised to revolutionize the delivery process is especially beneficial for those with a fear of needles. A next-generation COVID-19 mucosal vaccine is set to be a game-changer not only when delivering [...]
Scientists Develop All-in-One Solution To Catch and Destroy “Forever Chemicals”
A new water treatment system developed by UBC researchers efficiently removes and destroys PFAS pollutants using a dual-action catalyst, offering a sustainable and cost-effective solution for water purification challenges. Chemical engineers at the University of [...]
New method accelerates drug discovery from years to months
Researchers from the University of Cincinnati College of Medicine and Cincinnati Children's Hospital have found a new method to increase both speed and success rates in drug discovery. The study, published Aug. 30 in [...]
A new smart mask analyzes your breath to monitor your health
Your breath can give away a lot about you. Each exhalation contains all sorts of compounds, including possible biomarkers for disease or lung conditions, that could give doctors a valuable insight into your health. [...]
Study reveals the role of blood clotting in COVID-19
In a study that reshapes what we know about COVID-19 and its most perplexing symptoms, scientists have discovered that the blood coagulation protein fibrin causes the unusual clotting and inflammation that have become hallmarks [...]
A Novel Cancer Vaccine Combining Nano-11 and ADU-S100
In a recent article published in npj Vaccines, researchers detailed the development of a novel cancer vaccine that combines a plant-derived nanoparticle adjuvant, Nano-11, with a clinically tested STING agonist, ADU-S100. The primary objective was [...]
AI spots cancer and viral infections with nanoscale precision
Researchers have developed an artificial intelligence which can differentiate cancer cells from normal cells, as well as detect the very early stages of viral infection inside cells. The findings, published today in a study [...]
Tiny shards of plastic are increasingly infiltrating our brains, study says
Human brain samples collected at autopsy in early 2024 contained more tiny shards of plastic than samples collected eight years prior, according to a preprint posted online in May. A preprint is a study which has not yet [...]
Scientists Have Discovered Strange DNA in Our Brains – and It Could Be Shortening Our Lives
According to the research, these mitochondrial DNA insertions could be linked to early death. Mitochondria in brain cells frequently insert their DNA into the nucleus, potentially impacting lifespan, as those with more insertions were found to [...]
Watch Out After a Hospital Stay: You Could Be Exposing Your Family to Superbugs
Research indicates hospitals contribute to the local spread of antibiotic-resistant infections. A recent study published in the journal Infection Control & Hospital Epidemiology by the Society for Healthcare Epidemiology of America suggests that family members of [...]
Molecular Trickery: How COVID-19 Silently Sabotages the Human Immune System
Researchers have discovered that SARS-CoV-2 manipulates the human immune system by forcing cells to produce non-functional proteins, hindering the body’s antiviral defenses. This groundbreaking study by teams from prestigious Brazilian universities highlights potential targets for new COVID-19 treatments, [...]