For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of “strange metals”. Now a breakthrough has been achieved.
Superconductors allow electrical current to flow without any resistance – but only below a certain critical temperature. Many materials have to be cooled down to almost absolute zero, while some materials keep their superconducting properties up to much higher temperatures. How this “high-temperature superconductivity” works and how it is possible to develop new materials that are superconductors even at normal room temperature is still one of the great mysteries of modern physics.
The key to success could be research on “strange metals”. These are special materials whose electrical resistance shows a very unusual temperature behaviour. This phenomenon is closely related to superconductivity: many classes of high-temperature superconductors exhibit this “strange metal” behavior. Now there has been a major breakthrough: a research team from the TU Wien (Vienna, Austria) and Rice University (Houston, Texas) has developed a new process that allows extremely thin layers of such materials to be produced and then optically analyzed. In this way, important data about these materials are obtained that cannot be measured otherwise, which may lead to the development of better materials and new theories of high-temperature superconductivity.
Strange Metals as the Key to Superconductivity
“Already in 1987, the Nobel Prize in Physics was awarded for the discovery of high-temperature superconductivity, but even today our understanding of this phenomenon is still poor”, says Prof. Silke Bühler-Paschen from the Institute of Solid State Physics at Vienna University of Technology. “However, we know that strange metals are closely related to this technologically important class of superconductors.” Above their critical temperature, high-temperature superconductors show a relationship between temperature and resistance that is completely different from that of ordinary metals. “In contrast to simple metals such as copper or gold, the electrical resistance in strange metals does not appear to be caused by the thermal motion of the atoms, but by certain quantum fluctuations,” says Bühler-Paschen.
To confirm this assumption and to find out more about the nature of quantum fluctuations, not only the temperature dependence of the resistance, but also its frequency dependence must be investigated. The best way to do this is irradiating the material with light in the appropriate frequency range.
A material made of ytterbium, rhodium and silicon (YbRh2Si2), which is known for its particularly pronounced “strange metal” behaviour, was selected for the investigations. To study this material, radiation in the terahertz range is required.
“At this point, things became technologically challenging,” says Silke Bühler-Paschen. “High-precision measurements are only possible in transmission, that is, when the material is penetrated by the terahertz radiation. While electrically insulating materials usually allow terahertz radiation to pass, metals strongly reflect and absorb this type of radiation. Only if an extremely thin layer of the material is available, sufficient terahertz radiation will pass and thus enable precise measurements.”
Developing a New Manufacturing Process
In the clean room laboratories at TU Wien, a new complex molecular beam epitaxy process was developed to produce thin layers of this material: “Ytterbium, rhodium and silicon are evaporated in precisely the right ratio. Atom by atom, these materials impinge on a substrate,” says Maxwell Andrews (Institute for Solid State Electronics, TU Vienna). “If all parameters are set correctly, YbRh2Si2 grows in atomic layers. By choosing the right duration of the growth process, you can achieve exactly the desired layer thickness.”
“The decisive breakthrough was finding a perfectly fitting substrate on which to apply these layers – namely germanium,” says Lukas Prochaska, one of the three leading doctoral students in the team. “The crystal structure of germanium fits geometrically perfectly the arrangement of the Ytterbium atoms. This allowed us to grow thin films of excellent quality.”
Understanding the Movement of Charge Carriers
PhD student Xinwei Li in the Kono group at Rice University then performed challenging high-precision tetahertz measurements on the thin films. The analysis of the data, in which Rice theorist Qimiao Si also played a major role, yielded decisive new evidence: “Our assumption that quantum-critical charge fluctuations play an important role has now been confirmed,” says Silke Bühler-Paschen. “We have come full circle here: In 2004, we were able to show that the “strange metal” behavior in this material is accompanied by a sudden change in the charge carrier concentration. At that time, Qimiao Si and I had already recognized the need for dynamical measurements, but the technology to realize them was not available. Now we were finally able to scrutinize and understand this process.”
The new results indicate how to describe these unusual material effects. “Our new ideas can also be transferred to other classes of high-temperature superconductors,” explains Bühler-Paschen. “We hope that this will lead to a new theory of high-temperature superconductivity, and to the design of better superconductors with even higher critical temperatures; this would be a tremendous technological success.”
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
The European Space Agency is fast-tracking a new mission called Ramses, which will fly to near-Earth asteroid 99942 Apophis and join the space rock in 2029 when it comes very close to our planet — closer even than the region where geosynchronous satellites sit.
Ramses is short for Rapid Apophis Mission for Space Safety and, as its name suggests, is the next phase in humanity’s efforts to learn more about near-Earth asteroids (NEOs) and how we might deflect them should one ever be discovered on a collision course with planet Earth.
In order to launch in time to rendezvous with Apophis in February 2029, scientists at the European Space Agency have been given permission to start planning Ramses even before the multinational space agency officially adopts the mission. The sanctioning and appropriation of funding for the Ramses mission will hopefully take place at ESA’s Ministerial Council meeting (involving representatives from each of ESA’s member states) in November of 2025. To arrive at Apophis in February 2029, launch would have to take place in April 2028, the agency says.
This is a big deal because large asteroids don’t come this close to Earth very often. It is thus scientifically precious that, on April 13, 2029, Apophis will pass within 19,794 miles (31,860 kilometers) of Earth. For comparison, geosynchronous orbit is 22,236 miles (35,786 km) above Earth’s surface. Such close fly-bys by asteroids hundreds of meters across (Apophis is about 1,230 feet, or 375 meters, across) only occur on average once every 5,000 to 10,000 years. Miss this one, and we’ve got a long time to wait for the next.
When Apophis was discovered in 2004, it was for a short time the most dangerous asteroid known, being classified as having the potential to impact with Earth possibly in 2029, 2036, or 2068. Should an asteroid of its size strike Earth, it could gouge out a crater several kilometers across and devastate a country with shock waves, flash heating and earth tremors. If it crashed down in the ocean, it could send a towering tsunami to devastate coastlines in multiple countries.
Over time, as our knowledge of Apophis’ orbit became more refined, however, the risk of impact greatly went down. Radar observations of the asteroid in March of 2021 reduced the uncertainty in Apophis’ orbit from hundreds of kilometers to just a few kilometers, finally removing any lingering worries about an impact — at least for the next 100 years. (Beyond 100 years, asteroid orbits can become too unpredictable to plot with any accuracy, but there’s currently no suggestion that an impact will occur after 100 years.) So, Earth is expected to be perfectly safe in 2029 when Apophis comes through. Still, scientists want to see how Apophis responds by coming so close to Earth and entering our planet’s gravitational field.
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“There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, who is the Director of Research at CNRS at Observatoire de la Côte d’Azur in Nice, France, in a statement. “Nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface.”
The Goldstone radar’s imagery of asteroid 99942 Apophis as it made its closest approach to Earth, in March 2021. (Image credit: NASA/JPL–Caltech/NSF/AUI/GBO)
By arriving at Apophis before the asteroid’s close encounter with Earth, and sticking with it throughout the flyby and beyond, Ramses will be in prime position to conduct before-and-after surveys to see how Apophis reacts to Earth. By looking for disturbances Earth’s gravitational tidal forces trigger on the asteroid’s surface, Ramses will be able to learn about Apophis’ internal structure, density, porosity and composition, all of which are characteristics that we would need to first understand before considering how best to deflect a similar asteroid were one ever found to be on a collision course with our world.
Besides assisting in protecting Earth, learning about Apophis will give scientists further insights into how similar asteroids formed in the early solar system, and, in the process, how planets (including Earth) formed out of the same material.
One way we already know Earth will affect Apophis is by changing its orbit. Currently, Apophis is categorized as an Aten-type asteroid, which is what we call the class of near-Earth objects that have a shorter orbit around the sun than Earth does. Apophis currently gets as far as 0.92 astronomical units (137.6 million km, or 85.5 million miles) from the sun. However, our planet will give Apophis a gravitational nudge that will enlarge its orbit to 1.1 astronomical units (164.6 million km, or 102 million miles), such that its orbital period becomes longer than Earth’s.
It will then be classed as an Apollo-type asteroid.
Ramses won’t be alone in tracking Apophis. NASA has repurposed their OSIRIS-REx mission, which returned a sample from another near-Earth asteroid, 101955 Bennu, in 2023. However, the spacecraft, renamed OSIRIS-APEX (Apophis Explorer), won’t arrive at the asteroid until April 23, 2029, ten days after the close encounter with Earth. OSIRIS-APEX will initially perform a flyby of Apophis at a distance of about 2,500 miles (4,000 km) from the object, then return in June that year to settle into orbit around Apophis for an 18-month mission.
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Furthermore, the European Space Agency still plans on launching its Hera spacecraft in October 2024 to follow-up on the DART mission to the double asteroid Didymos and Dimorphos. DART impacted the latter in a test of kinetic impactor capabilities for potentially changing a hazardous asteroid’s orbit around our planet. Hera will survey the binary asteroid system and observe the crater made by DART’s sacrifice to gain a better understanding of Dimorphos’ structure and composition post-impact, so that we can place the results in context.
The more near-Earth asteroids like Dimorphos and Apophis that we study, the greater that context becomes. Perhaps, one day, the understanding that we have gained from these missions will indeed save our planet.
