Team makes superconductors the “Holy Grail”

For the first time, researchers have created a material that is superconducting at room temperature.

The development of superconducting materials – without electrical resistance and the emission of the magnetic field at room temperature – is the “holy grail” of condensed matter physics, says Ranga Dias, assistant professor of mechanical engineering and of physics and astronomy at the University of Rochester.

Searched for more than a century, such materials can “definitely change the world as we know it,” says Dias.

Break down barriers with superconductors

To set the new record, Dias and his research team combined hydrogen with carbon and sulfur to photochemically synthesize simple carbon-containing sulfur hydride from organic production in a diamond anvil cell, a research device used to study tiny amounts of material under extremely high pressure.

The carbonaceous sulfur hydride exhibited superconductivity at about 58 degrees Fahrenheit and a pressure of about 39 million pounds per square inch (psi).

“Due to the limits of low temperatures, materials with such extraordinary properties have not changed the world in the way many imagined. However, our discovery will break down those barriers and open the door to many potential applications, ”says Dias, who is also involved in the university’s materials science and high-energy physics programs.

Applications include:

• Power grids that transmit electricity without losing up to 200 million megawatt hours (MWh) of energy that is now created due to the resistance in the wires
• A new way to power floating trains and other means of transport
• Medical imaging and scanning techniques such as MRI and magnetocardiography
• Faster, more efficient electronics for digital logic and storage device technology

“We live in a semiconductor society, and with this type of technology you can turn society into a superconducting society where you never need things like batteries again,” said Ashkan Salamat of the University of Nevada in Las Vegas, co-author of the discovery.

The amount of superconducting material produced by the diamond anvil cells is measured in picoliters – roughly the size of a single inkjet particle.

The next challenge, says Dias, is to find ways to produce the superconducting materials at room temperature at lower pressures so that they can be economically produced in larger volumes. Compared to the millions of pounds of pressure created in diamond anvil cells, the earth’s atmospheric pressure at sea level is about 15 psi.

The power of superconducting materials

Superconductivity was first discovered in 1911 and gives materials two key properties.

The electrical resistance disappears. And any semblance of a magnetic field is expelled due to a phenomenon called the Meissner effect. The magnetic field lines must run around the superconducting material, which makes it possible to levitate such materials, which could be used for smooth high-speed trains, so-called magnetic levitation trains.

Powerful superconducting electromagnets are already an integral part of magnetic levitation trains, magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) machines, particle accelerators, and other advanced technologies, including early quantum supercomputers.

However, the superconducting materials used in the devices usually only work at extremely low temperatures – lower than all natural temperatures on earth. This limitation makes it costly to maintain – and too costly to extend to other potential applications.

“The cost of keeping these materials at cryogenic temperatures is so high that you can’t really get the full benefit from them,” says Dias.

Previously, the highest temperature for a superconducting material was reached last year in the laboratory of Mikhail Eremets at the Max Planck Institute for Chemistry in Mainz and the Russell Hemley group at the University of Illinois in Chicago. This team reported superconductivity at -10 to 8 degrees Fahrenheit using lanthanum superhydride.

Researchers have also examined copper oxides and iron-based chemicals as potential candidates for high temperature superconductors in recent years. Hydrogen – the most abundant element in the universe – also offers a promising building block.

“To have a high temperature superconductor, you want stronger bonds and light elements. Those are the two basic criteria, ”says Dias. “Hydrogen is the lightest material and hydrogen bonding is one of the strongest.

“It is believed that solid metallic hydrogen has a high Debye temperature and strong electron-phonon coupling, which is required for superconductivity at room temperature,” says Dias.

However, extremely high pressures are required to bring pure hydrogen into a metallic state. This was first achieved in 2017 in a laboratory by Isaac Silvera and Dias, professor at Harvard University, and subsequently as a postdoc in Silvera’s laboratory.

“Paradigm shift”

Therefore, Dias’ laboratory has followed a “paradigm shift” in its approach, using hydrogen-rich materials as an alternative, which mimic the elusive superconducting phase of pure hydrogen and can be metallized at much lower pressures.

First, the laboratory combined yttrium and hydrogen. The resulting yttrium superhydride exhibited superconductivity at what was then a record temperature of about 12 degrees Fahrenheit and a pressure of about 26 million pounds per square inch.

Next, the lab examined covalent hydrogen-rich organic materials.

This work resulted in the carbonaceous sulfur hydride. “This presence of carbon is extremely important here,” the researchers report. Another “compositional tuning” of this combination of elements could be the key to achieving superconductivity at even higher temperatures, they add.

The research appears in nature. Other co-authors are the University of Rochester, Intel Corporation and the University of Nevada in Las Vegas.

Support for the project came from the National Science Foundation and the US Department of Energy’s Stockpile Stewardship Academic Alliance Program and the Office of Science, Fusion Energy Sciences.

Dias and Salamat have founded a new company called Unearthly Materials to find a way to produce superconductors at room temperature that can be manufactured in a scalable manner at ambient pressure. Patents are pending.

Source: University of Rochester