Correlated Electrons “Tango” in a Perovskite Oxide at the Extreme Quantum Limit
Originally published by Oak Ridge National Laboratory.
A team led by the Department of Energy’s Oak Ridge National Laboratory has found a rare quantum material in which electrons move in coordinated ways, essentially “dancing.” Straining the material creates an electronic band structure that sets the stage for exotic, more tightly correlated behavior — akin to tangoing — among Dirac electrons, which are especially mobile electric charge carriers that may someday enable faster transistors. The results are published in the journal Science Advances.
“We combined correlation and topology in one system,” said co-principal investigator Jong Mok Ok, who conceived the study with principal investigator Ho Nyung Lee of ORNL. Topology probes properties that are preserved even when a geometric object undergoes deformation, such as when it is stretched or squeezed. “The research could prove indispensable for future information and computing technologies,” added Ok, a former ORNL postdoctoral fellow.
In conventional materials, electrons move predictably (for example, lethargically in insulators or energetically in metals). In quantum materials in which electrons strongly interact with each other, physical forces cause the electrons to behave in unexpected but correlated ways; one electron’s movement forces nearby electrons to respond.
To study this tight tango in topological quantum materials, Ok led the synthesis of an extremely stable crystalline thin film of a transition metal oxide. He and colleagues made the film using pulsed-laser epitaxy and strained it to compress the layers and stabilize a phase that does not exist in the bulk crystal. The scientists were the first to stabilize this phase.
Using theory-based simulations, co-principal investigator Narayan Mohanta, a former ORNL postdoctoral fellow, predicted the band structure of the strained material. “In the strained environment, the compound that we investigated, strontium niobate, a perovskite oxide, changes its structure, creating a special symmetry with a new electron band structure,” Mohanta said.
Different states of a quantum mechanical system are called “degenerate” if they have the same energy value upon measurement. Electrons are equally likely to fill each degenerate state. In this case, the special symmetry results in four states occurring in a single energy level.
“Because of the special symmetry, the degeneracy is protected,” Mohanta said. “The Dirac electron dispersion that we found here is new in a material.” He performed calculations with Satoshi Okamoto, who developed a model for discovering how crystal symmetry influences band structure.
“Think of a quantum material under a magnetic field as a 10-story building with residents on each floor,” Ok posited. “Each floor is a defined, quantized energy level. Increasing the field strength is akin to pulling a fire alarm that drives all the residents down to the ground floor to meet at a safe place. In reality, it drives all the Dirac electrons to a ground energy level called the extreme quantum limit.”
Lee added, “Confined here, the electrons crowd together. Their interactions increase dramatically, and their behavior becomes interconnected and complicated.” This correlated electron behavior, a departure from a single-particle picture, sets the stage for unexpected behavior, such as electron entanglement. In entanglement, a state Einstein called “spooky action at a distance,” multiple objects behave as one. It is key to realizing quantum computing.
“Our goal is to understand what will happen when electrons enter the extreme quantum limit, where we find phenomena we still don’t understand,” Lee said. “This is a mysterious area.”
Speedy Dirac electrons hold promise in materials including graphene, topological insulators and certain unconventional superconductors. ORNL’s unique material is a Dirac semimetal, in which electron valence and conduction bands cross and this topology yields surprising behavior. Ok led measurements of the Dirac semimetal’s strong electron correlations.
“We found the highest electron mobility in oxide-based systems,” Ok said. “This is the first oxide-based Dirac material reaching the extreme quantum limit.”
That bodes well for advanced electronics. Theory predicts that it should take about 100,000 tesla (a unit of magnetic measurement) for electrons in conventional semiconductors to reach the extreme quantum limit. The researchers took their strain-engineered topological quantum material to Eun Sang Choi of the National High Magnetic Field Laboratory at the University of Florida to see what it would take to drive electrons to the extreme quantum limit. There, he measured quantum oscillations showing the material would require only 3 tesla to achieve that.
Other specialized facilities allowed the scientists to experimentally confirm the behavior Mohanta predicted. The experiments occurred at low temperatures so that electrons could move around without getting bumped by atomic-lattice vibrations. Jeremy Levy’s group at the University of Pittsburgh and the Pittsburgh Quantum Institute confirmed quantum transport properties. With synchrotron x-ray diffraction, Hua Zhou at the Advanced Photon Source, a DOE Office of Science user facility at Argonne National Laboratory, confirmed that the material’s crystallographic structure stabilized in the thin film phase yielded the unique Dirac band structure. Sangmoon Yoon and Andrew Lupini, both of ORNL, conducted scanning transmission electron microscopy experiments at ORNL that showed that the epitaxially grown thin films had sharp interfaces between layers and that the transport behaviors were intrinsic to strained strontium niobate.
“Until now, we could not fully explore the physics of the extreme quantum limit due to the difficulties in pushing all electrons to one energy level to see what would happen,” Lee said. “Now, we can push all the electrons to this extreme quantum limit by applying only a few tesla of magnetic field in a lab, accelerating our understanding of quantum entanglement.”
The title of the Science Advances paper is “Correlated Oxide Dirac Semimetal in the Extreme Quantum Limit.”
The DOE Office of Science supported the research. High magnetic field measurements were performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation and the state of Florida. The research used resources of the Advanced Photon Source, a DOE Office of Science user facility at Argonne National Laboratory; its extraordinary facility operations to provide beam time during the pandemic were supported in part by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on the response to COVID-19, with funding provided by the Coronavirus CARES Act.
UT-Battelle manages ORNL for the Department of Energy’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
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Kia’s electric SUVs are taking over. The EV3 is the best-selling retail EV in the UK this year, giving Kia its strongest sales start since it arrived 34 years ago. And it’s not just in the UK. Kia just had its best first quarter globally since it started selling cars in 1962.
Kia EV3 is the best-selling EV in the UK through March
In March, Kia sold a record nearly 20,000 vehicles in the UK, making it the fourth best-selling brand. It was also the second top-seller of electrified vehicles (EVs, PHEVs, and HEVs), accounting for over 55% of sales.
The EV3 remained the best-selling retail EV in the UK last month. Including the EV6, three-row EV9, and Niro EV, electric vehicles represented 21% of Kia’s UK sales in March.
Kia said the EV3 “started with a bang” in January, darting out as the UK’s most popular EV in retail sales. Through March, Kia’s electric SUV has held on to the crown. With the EV3 rolling out, Kia sold over 7,000 electric cars through March, nearly 50% more than in Q1 2024.
The EV3 was the best-selling retail EV in the UK in the first quarter and the fourth best-selling EV overall, including commercial vehicles.
Starting at £33,005 ($42,500), Kia said it’s the “brand’s most affordable EV yet.” It’s available with two battery packs, 58.3 kWh or 81.48 kWh, good for 430 km (270 miles) and 599 km (375 miles) of WLTP range, respectively.
With new EVs on the way, this could be just the start. Kia is launching several new EVs in the UK this year, including the EV4 sedan (and hatchback) and EV5 SUV. It also confirmed that the first PV5 electric vans will be delivered to customers by the end of the year.
Electrek’s Take
Globally, Kia sold a record 772,351 vehicles in the first quarter, its best since it started selling cars in 1962. With the new EV4, the brand’s first electric sedan and hatchback, launching this year, Kia looks to build on its momentum in 2025.
Kia has also made it very clear that it wants to be a global leader in the electric van market with its new Platform Beyond Vehicle (PBV) business, starting with the PV5 later this year.
Earlier today, we learned Kia’s midsize electric SUV, the EV5, is the fourth best-selling EV in Australia through March, outselling every BYD vehicle (at least for now). The EV5 is rolling out to new markets this year, including Canada, the UK, South Korea, and Mexico. However, it will not arrive in the US.
For those in the US, there are still a few Kia EVs to look forward to. Kia is launching the EV4 globally, including in the US, later this year. Although no date has been set, Kia confirmed the EV3 is also coming. It’s expected to arrive in mid-2026.
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Podcast: Tesla’s disastrous deliveries, more Trump tariffs, EV delivery numbers, and more
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Charging your EV in freezing weather could soon become dramatically faster, thanks to a big breakthrough from the University of Michigan engineers.
Neil Dasgupta, U-M associate professor of mechanical engineering and materials science and engineering and corresponding author of a study published in Joule, and his team have developed an innovative battery structure and coating that can boost lithium-ion EV battery charging speeds by a whopping 500%, even at frigid temperatures as low as 14F (-10C). “Charging an EV battery takes 30 to 40 minutes even for aggressive fast charging, and that time increases to over an hour in the winter,” Dasgupta explained. “This is the pain point we want to address.”
Freezing weather has traditionally been harsh on EV batteries because it slows down the movement of lithium ions, resulting in slower charging speeds and reduced battery life. Automakers have tried thickening battery electrodes to extend driving range, but this makes some of the lithium hard to access, making charging even slower.
Previously, Dasgupta’s group sped up battery charging using lasers to carve pathways around 40 microns in size into the graphite anode. This allowed lithium ions to reach deeper into the battery more quickly. However, cold-weather performance still lagged because a chemical layer formed on the electrodes, blocking the ions. Dasgupta compares this barrier to “trying to cut cold butter,” making charging inefficient.
To solve this, the team coated the battery with a thin, glassy material made of lithium borate-carbonate—only 20 nanometers thick—which prevented the problematic chemical layer from forming. Combined with the microscopic channels, the results were groundbreaking: the modified batteries retained 97% of their capacity even after 100 fast-charging cycles in freezing temperatures.
“We envision this approach as something that EV battery manufacturers could adopt without major changes to existing factories,” Dasgupta noted. “For the first time, we’ve shown a pathway to simultaneously achieve extreme fast charging at low temperatures, without sacrificing the energy density of the lithium-ion battery.”
This innovation could tackle one of the biggest concerns holding potential EV buyers back.
The new battery tech is moving closer to commercialization, supported by the Michigan Economic Development Corporation’s Michigan Translational Research and Commercialization (MTRAC) Advanced Transportation Innovation Hub. The research devices were built at U-M’s Battery Lab and studied with help from the Michigan Center for Materials Characterization.
U-M Innovation Partnerships assisted the team in applying for patents, and Arbor Battery Innovations has licensed the technology for market deployment. Dasgupta and the University of Michigan hold financial stakes in Arbor Battery Innovations.
Read more: California now has nearly 50% more EV chargers than gas nozzles
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