Rare “Lazarus Superconductivity” Observed in Rediscovered Material

 
Researchers from the University of Maryland, the National Institute of Standards and Technology (NIST), the National High Magnetic Field Laboratory (National MagLab) and the University of Oxford have observed a rare phenomenon called re-entrant superconductivity in the material uranium ditelluride. The discovery furthers the case for uranium ditelluride as a promising material for use in quantum computers.

A team of researchers has observed a rare phenomenon called re-entrant superconductivity in the material uranium ditelluride. Nicknamed “Lazarus superconductivity,” the phenomenon occurs when a superconducting state arises, breaks down, then re-emerges in a material due to a change in a specific parameter—in this case, the application of a very strong magnetic field. The discovery furthers the case for uranium ditelluride as a promising material for use in quantum computers. Image credit: Emily Edwards/JQI (Click image to download hi-res version.)

A team of researchers has observed a rare phenomenon called re-entrant superconductivity in the material uranium ditelluride. Nicknamed “Lazarus superconductivity,” the phenomenon occurs when a superconducting state arises, breaks down, then re-emerges in a material due to a change in a specific parameter—in this case, the application of a very strong magnetic field. The discovery furthers the case for uranium ditelluride as a promising material for use in quantum computers. Image credit: Emily Edwards/JQI (Click image to download hi-res version.)

Nicknamed “Lazarus superconductivity” after the biblical figure who rose from the dead, the phenomenon occurs when a superconducting state arises, breaks down, then re-emerges in a material due to a change in a specific parameter—in this case, the application of a very strong magnetic field. The researchers published their results on October 7, 2019, in the journal Nature Physics.

Once dismissed by physicists for its apparent lack of interesting physical properties, uranium ditelluride is having its own Lazarus moment. The current study is the second in as many months (both published by members of the same research team) to demonstrate unusual and surprising superconductivity states in the material.

“This is a very recently discovered superconductor with a host of other unconventional behavior, so it's already weird,” said Nicholas Butch, an adjunct assistant professor of physics at UMD and a physicist at the NIST Center for Neutron Research. “[Lazarus superconductivity] almost certainly has something to do with the novelty of the material. There's something different going on in there.”

The previous research, published on August 16, 2019 in the journal Science, described the rare and exotic ground state known as spin-triplet superconductivity in uranium ditelluride. The discovery marked the first clue that uranium ditelluride is worth a second look, due to its unusual physical properties and its high potential for use in quantum computers.

“This is indeed a remarkable material and it’s keeping us very busy,” said Johnpierre Paglione, a professor of physics at UMD, the director of UMD’s Center for Nanophysics and Advanced Materials (CNAM; soon to be renamed the Quantum Materials Center) and a co-author of the paper. “Uranium ditelluride may very well become the ‘textbook’ spin-triplet superconductor that people have been seeking for dozens of years and it likely has more surprises in store. It could be the next strontium ruthenate—another proposed spin-triplet superconductor that has been studied for more than 25 years.”

Superconductivity is a state in which electrons travel through a material with perfect efficiency. By contrast, copper—which is second only to silver in terms of its ability to conduct electrons—loses roughly 20% power over long-distance transmission lines, as the electrons bump around within the material during travel.

Lazarus superconductivity is especially strange, because strong magnetic fields usually destroy the superconducting state in the vast majority of materials. In uranium ditelluride, however, a strong magnetic field coupled with specific experimental conditions caused Lazarus superconductivity to arise not just once, but twice.

For Butch, Paglione and their team, the discovery of this rare form of superconductivity in uranium ditelluride was serendipitous; the study’s lead author, CNAM Research Associate Sheng Ran, synthesized the crystal accidentally while attempting to produce another uranium-based compound. The team decided to try some experiments anyway, even though previous research on the compound hadn’t yielded anything unusual.

The team’s curiosity was soon rewarded many times over. In the earlier Science paper, the researchers reported that uranium ditelluride’s superconductivity involved unusual electron configurations called spin triplets, in which pairs of electrons are aligned in the same direction. In the vast majority of superconductors, the orientations—called spins—of paired electrons point in opposite directions. These pairs are (somewhat counterintuitively) called singlets. Magnetic fields can more easily disrupt singlets, killing superconductivity.

Spin triplet superconductors, however, can withstand much higher magnetic fields. The team’s early findings led them to the National MagLab, where a unique combination of very high-field magnets, capable instrumentation and resident expertise allowed the researchers to push uranium ditelluride even further.

At the lab, the team tested uranium ditelluride in some of the highest magnetic fields available. By exposing the material to magnetic fields up to 65 teslas—more than 30 times the strength of a typical MRI magnet—the team attempted to find the upper limit at which the magnetic fields crushed the material’s superconductivity. Butch and his team also experimented with orienting the uranium ditelluride crystal at several different angles in relation to the direction of the magnetic field.

At about 16 teslas, the material’s superconducting state abruptly changed. While it died in most of the experiments, it persisted when the crystal was aligned at a very specific angle in relation to the magnetic field. This unusual behavior continued until about 35 teslas, at which point all superconductivity vanished and the electrons shifted their alignment, entering a new magnetic phase.

As the researchers increased the magnetic field while continuing to experiment with angles, they found that a different orientation of the crystal yielded yet another superconducting phase that persisted to at least 65 teslas, the maximum field strength the team tested. It was a record-busting performance for a superconductor and marked the first time two field-induced superconducting phases have been found in the same compound. 

Instead of killing superconductivity in uranium ditelluride, high magnetic fields appeared to stabilize it. While it is not yet clear exactly what is happening at the atomic level, Butch said the evidence points to a phenomenon fundamentally different than anything scientists have seen to date.

“I'm going to go out on a limb and say that these are probably different—quantum mechanically different—from other superconductors that we know about,” Butch said. “It is sufficiently different, I think, to expect it will take a while to figure out what's going on.”

On top of its convention-defying physics, uranium ditelluride shows every sign of being a topological superconductor, as are other spin-triplet superconductors, Butch added. Its topological properties suggest it could be a particularly accurate and robust component in the quantum computers of the future.

“The discovery of this Lazarus superconductivity at record-high fields is likely to be among the most important discoveries to emerge from this lab in its 25-year history,” said National MagLab Director Greg Boebinger. “I would not be surprised if unraveling the mysteries of uranium ditelluride leads to even stranger manifestations of superconductivity in the future.”

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This release was adapted from text provided by the National High Magnetic Field Laboratory.

In addition to Butch, Paglione and Ran, UMD-affiliated co-authors of the research paper include physics postdoctoral researcher Yun Suk Eo; physics graduate students I-Lin LiuDaniel Campbell and Christopher Eckberg; undergraduate physics major Paul Neves, physics faculty assistant Wesley Fuhrman; CNAM (QMC) Assistant Research Scientist Hyunsoo Kim and CNAM (QMC) Associate Research Scientist Shanta Saha.

The research paper, “Extreme magnetic field-boosted superconductivity,” Sheng Ran, I-Lin Liu, Yun Suk Eo, Daniel Campbell, Paul Neves, Wesley Fuhrman, Shanta Saha, Christopher Eckberg, Hyunsoo Kim, Johnpierre Paglione, David Graf, Fedor Balakirev, John Singleton and Nicholas Butch, was published in the journal Nature Physics on October 7, 2019.

This work was supported by the Schmidt Science Fellows program (in partnership with the Rhodes Trust), the National Science Foundation (Award Nos. DMR-1610349, DMR-1157490, DMR-1644779), the U.S. Department of Energy (Award No. DE-SC-0019154), the Gordon and Betty Moore Foundation’s EPiQS Initiative (Award No. GBMF4419), and the State of Florida. The content of this article does not necessarily reflect the views of these organizations.

Media Relations Contact: Matthew Wright, 301-405-9267, This email address is being protected from spambots. You need JavaScript enabled to view it.

Original story: https://cmns.umd.edu/news-events/features/4500

 

Hans R. Griem, 1928-2019

Prof. Emeritus Hans R. Griem, a noted expert in high-temperature plasmas and spectroscopy, died on October 2, 2019.

Prof. Griem received his Ph.D. from the Universität of Kiel, Germany, in 1954 and accepted a Fulbright Fellowship working on upper atmospheric physics at UMD. He returned to Universität Kiel for a two-year appointment before joining the UMD faculty in 1957.   He was well known for his research on radiation from highly ionized atoms in high temperature plasmas, and for his work on spectral line broadening (and shifts) in dense plasmas.  He was a consultant with Los Alamos National Laboratory during most of his career, and retired from UMD in 1994.

He was a fellow of the American Physical Society and a referee for several journals, including Physical Review Letters.  Among his accolades were a Guggenheim Fellowship, a Humboldt Award and the William F. Meggers Award of the Optical Society.  In 1991 he received the James Clerk Maxwell Prize in Plasma Physics for "his numerous contributions to experimental plasma physics and spectroscopy, particularly in the area of improved diagnostic methods for high temperature plasmas, and for his books on plasma spectroscopy and spectral line broadening in plasmas that have become standard references in the field."

Prof. Griem was instrumental in founding the UMD Institute Research in Electronics and Applied Physics, and served as one of the first directors of IREAP. He advised over 40 doctoral students in his time at UMD.

Jim Griffin, Hans Griem and Doug Currie in 2001.

In The Washington Post obituary published Oct. 6, 2019, the Griem family kindly directed donations in Prof. Griem's name to UMD Physics.

https://www.legacy.com/amp/obituaries/washingtonpost/194085051 

Joel Dahlin Receives Ronald Davidson Award

Joel Dahlin

Alumnus Joel Dahlin, who earned his Ph.D. in 2015, has received the 2019 Ronald C. Davidson Award for Plasma Physics from AIP Publishing. Dahlin, who was advised by Distinguished University Professor James Drake and Marc Swisdak of the Institute for Research in Electronics and Applied Physics­­, is now a postdoctoral fellow at the NASA Goddard Space Flight Center.

AIP Publishing sponsors the award in collaboration with the American Physical Society’s Division of Plasma Physics (APS-DPP), to recognize one researcher each year whose outstanding work has been published in the journal Physics of Plasmas.

"AIP Publishing and Physics of Plasmas are delighted to award Joel T. Dahlin the 2019 Ronald C. Davidson Award for Plasmas Physics," said Jason Wilde, chief publishing officer at AIP Publishing. "Now in its fourth year, this award is in honor of the late Ron Davidson, the long-time Editor-in-Chief of Physics of Plasmas."

Dahlin is being honored for his article, "The mechanisms of electron heating and acceleration during magnetic reconnection," written with Drake and Swisdak. It was selected from the most highly cited and most highly downloaded articles published in Physics of Plasmas during the past five years. 

“It is a great honor to be recognized with an award bearing Ron Davidson’s name, given his broad and influential contributions to the field of plasma physics. Since my co-authors and I published our work, it has been exciting and deeply gratifying to see how other researchers have used and built on the ideas we laid out,” Dahlin said.

The paper explored the mechanisms for electron acceleration caused by collision-less magnetic reconnection in plasma with a magnetic guide field sufficient for adiabatic electron motion. In a follow-up paper, “Electron acceleration in three-dimensional magnetic reconnection with a guide field,” Physics of Plasmas 22, 100704 (2015), Dahlin and his co-authors showed a dramatic enhancement of energetic electron production in 3D systems where stochastic magnetic fields enable continuous access to volume-filling acceleration regions.

According to Spiro K. Antiochos of NASA GSFC, "Joel Dahlin's results on particle acceleration during magnetic reconnection, especially on the effects of a guide field, may well be the key to finally understanding two decades-old major puzzles in the plasma physics of solar flares: How are flares so efficient at accelerating electrons, and why does the acceleration occur only during the early, impulsive phase of a flare?”

Dahlin will be presented with the award during the 61st Annual Meeting of the APS Division of Plasma Physics on Tues., Oct. 22.

For more information, please see the AIP announcement here.

Quantum Materials Symposium to Showcase Local Expertise and Highlight Partnerships in D.C. Region

The University of Maryland held a one-day symposium focusing on local research into quantum materials—condensed matter systems that exhibit strong quantum effects and hold promise as potential components in next-generation computers, sensors and other devices on Sept. 26, 2019, in the Kim Engineering Building.  

Hosted by UMD’s Center for Nanophysics and Advanced Materials (CNAM)—which will be renamed the Quantum Materials Center next month—the event broght together researchers from the university’s Departments of Physics, Chemistry and Biochemistry, Electrical and Computer Engineering, and Materials Science and Engineering, in addition to researchers from the nearby National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences. Around 50 quantum materials researchers and institutional leaders were expected to attend.

CNAM Director and Professor of Physics Johnpierre Paglione, together with Joint Quantum Institute (JQI) Fellow and Assistant Professor of Physics James Williams, organized the event, which included talks on recent quantum materials research as well as reflections on collaborations that have formed among UMD researchers and also between researchers at UMD and area partners such as NIST.

“Fundamental studies of quantum materials play a critical role in not only supporting current development of quantum technologies, but also the discovery of new phenomena that hold promise for future applications,” Paglione said. “This symposium will bring together the top experts from our local community and will hopefully sprout new collaborations and partnerships.”

Amitabh Varshney, dean of UMD’s College of Computer, Mathematical, and Natural Sciences, and Robert Briber, associate dean of UMD’s A. James Clark School of Engineering, delivered their perspectives on campus initiatives in quantum science, including the newly formed Quantum Technology Center. Carl Williams, a JQI Fellow and the acting director of the Physical Measurement Laboratory at NIST, discussed aspects of the National Quantum Initiative, and Dan Neumann, group leader of neutron condensed matter science at the NIST Center for Neutron Research (NCNR), discussed the partnership between CNAM and NCNR, which recently led to the discovery of a superconductor that may be useful in future quantum computers.

“CNAM maintains strong interdisciplinary collaborations with researchers across several departments and institutes,” Paglione said. “Going forward, we want to strengthen those partnerships, which have contributed to the success of CNAM’s fundamental research on quantum materials.”

Jeffrey Lynn, a NIST Fellow and adjunct professor of physics at UMD, is the team leader for condensed matter physics at NCNR. He noted, “There have been longstanding multidisciplinary cooperative research collaborations between NIST and UMD in general, and the NCNR and CNAM in particular,” Lynn says. “In addition to the research output, these collaborations provide cross-institutional research capabilities for students, postdoctoral fellows, and scientific staff that are essential to perform the best quantum materials research.”

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Story by Chris Cesare, This email address is being protected from spambots. You need JavaScript enabled to view it.