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Breakthrough of the Year: The First Room Temperature Superconductor Created

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Levitating is a “standard” effect that is shown in most experiments related to superconductivity.

Scientists have created an unusual material that conducts electricity without any resistance at temperatures up to about 15 ° C. Yes, its electrical resistance is not just low, it is strictly zero. This is a new record for superconductivity, a phenomenon commonly associated with very low temperatures. The material itself used for experiments is currently poorly understood, but it shows the potential of a new class of superconductors, discovered in 2015.

However, the discovered superconductor has one serious limitation: it shows its unusual properties only at extremely high pressures, close to those that exist in the center of the Earth, which means that it will not have practical applications in the near future. Nonetheless, physicists hope this discovery could kick-start the development of zero-resistance materials that can operate at pressures more familiar to us.

Superconductors have a number of technological applications, from magnetic resonance imaging devices to mobile towers, and researchers are beginning to experiment with them in high-performance generators for wind turbines. But their usefulness is still limited by the need for bulky cryogenic plants. The oldest superconductors we know are capable of operating at atmospheric pressure, but only at very low temperatures. Even the most sophisticated of these – copper oxide ceramics – show superconducting properties only below 133 Kelvin (-140 ° C).

Superconductors operating at room temperature can literally turn the world around us. Imagine wires that have no heat loss: one thin cable can replace a chain of power lines. Non-heating electronics with an efficiency close to 100%. Levitating to create high-speed, efficient maglev. Eternal repositories of information. Superconductivity in our usual conditions can significantly transform all spheres of our activity, one way or another connected with electricity.


Superconductivity temperatures for various chemical elements and substances. The numbers are in degrees Kelvin, zero on this scale corresponds to -273.15 degrees Celsius.

New research published in the journal Nature October 14 is strong evidence of high-temperature superconductivity, says physicist Mikhail Eremets of the Max Planck Institute for Chemistry in Mainz, Germany, although he adds that he would like to see more “raw data” from the experiment. He says this confirms a series of experiments he began in 2015, when his group reported the first high-temperature, high-pressure superconductor, a hydrogen / sulfur compound that had zero resistance down to -70 ° C.

In 2018, it was shown that at high pressure, a compound of hydrogen and lanthanum is a superconductor at -13 ° C. However, the new result is the first to go beyond the psychological mark of zero degrees, as well as the first high-pressure superconductor, consisting of three elements, not two – the material consists of carbon, sulfur and hydrogen. The addition of the third element greatly expands the number of possible combinations that could be explored in future experiments to find new superconductors, said study co-author Ashkan Salamat, a physicist at the University of Nevada at Las Vegas. “We’ve discovered a whole new region” of research, he says.

 

Materials that are superconductive at high but not extreme pressures can already be used, says Madduri Somayazulu, a high-pressure materials specialist at Argonne National Laboratory in Lemont, Illinois. The study shows that by “judiciously choosing the third and possibly fourth elements” in a superconductor, it is possible in principle to reduce its operating pressure, he adds.

The work also confirms decades ago predictions by theoretical physicist Neil Ashcroft of Cornell University in Ithaca, New York, that hydrogen-rich materials could superconduct at temperatures close to ours. “I think very few people outside the high pressure community took his words seriously back then,” Somayazulu says.

Mysterious material


Experimental setup.

Physicist Ranga Diaz of the University of Rochester in New York, along with Salamat and others, placed a mixture of carbon, hydrogen and sulfur into a microscopic niche they carved between the tips of two diamonds. They then initiated chemical reactions in the sample using a high-power laser and squeezed the diamonds tightly, observing how the crystal formed.

They then cooled the resulting sample, discovering that the resistance to current passing through the material had dropped to zero – a clear indication that their crystal had become superconducting. Then they increased the pressure and found that the transition to the superconducting state began to occur at increasingly higher temperatures. Their best result was a transition temperature of 287.7 Kelvin, or about 14.5 degrees Celsius at 267 gigapascals, which is 2.6 million times the atmospheric pressure at sea level and close to the pressure at the Earth’s core.

The researchers also found some evidence that the crystal lost its magnetic field at the transition temperature, an important test for superconductivity. But much about this material still remains unknown, researchers warn. “There is still a lot to be found out,” says Eremets. Even the exact structure and chemical formula of the crystal are not yet known. “The higher the pressure, the smaller the sample becomes,” says Salamat. “That’s what makes these measurements really difficult.”

High-pressure superconductors, consisting of hydrogen and another element, are well studied. “And the researchers also performed the first of its kind computer simulations of a mixture of carbon, hydrogen and sulfur under high pressure,” says Eva Zurek, a computer chemist at the State University of New York at Buffalo. But she adds that the study cannot explain the exceptionally high superconducting temperatures observed by Diaz’s group. “I am confident that after this work is published, many theoretical and experimental groups will tackle this problem,” she says.

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