Researchers have created a superconducting material at both temperatures and pressures low enough for practical applications.
In a paper in the journal Nature, researchers from the University of Rochester, US, describe a nitrogen-doped lutetium hydride (NDLH) that exhibits superconductivity at 69 °F, or 20.6 °C, and 10 kilobars, or 145,000 pounds per square inch. Is. , or psi, of pressure.
Although 145,000 psi may still sound extraordinarily high – about 15 psi, or 1 bar, at sea level – strain engineering techniques are routinely used in chip manufacturing, for example, held together by internal chemical pressures. Including ingredients that are high, the study said.
“With this material, the dawn of ambient superconductivity and applicable technologies has arrived,” according to a team led by Ranga Dias, assistant professor of mechanical engineering and physics.
Scientists have been following this breakthrough in condensed matter physics for more than a century.
Superconducting materials have two key properties: the electrical resistance vanishes, and the magnetic fields that are expelled pass through the superconducting material. Such content can enable: 1. Power grids that transmit electricity without the loss of up to 200 million megawatt hours (MWh) of energy now caused by resistance in wires 2. Frictionless, high speed trains 3.
more affordable medical imaging and scanning technologies, such as MRI and magnetocardiography 4. Faster, more efficient electronics for digital logic and memory device technology Given the importance of the new discovery, Dias and his team went to unusual lengths to document their research and address criticisms that developed in the wake of the previous Nature paper, the study said, which led to the journal’s editors took it back.
According to Dias, the previous paper has been resubmitted to Nature with new data that validates the earlier work.
The new data was collected outside the laboratory, in front of an audience of scientists at Argonne and Brookhaven National Laboratories in the US, who witnessed the superconducting transition live.
A similar method has been adopted with the new paper as well.
“Everyone in the group was involved in doing the experiment,” says Dias. “It really was a collective effort.” Hydrides made by fusing rare earth metals with hydrogen, then adding nitrogen or carbon, have provided researchers in recent years with a “working recipe” for making superconducting materials.
In technical terms, the rare earth metal hydrides form a clathrate-like cage structure, where the rare earth metal ions act as carrier donors, providing enough electrons that will enhance the dissociation of H2 molecules. Nitrogen and carbon help stabilize the material.
Bottom line: Low pressure is needed for superconductivity to occur.
In addition to yttrium, researchers have used other rare earth metals. However, the resulting compounds become superconducting at temperatures or pressures that are still not practical for applications.
So, this time, Dias looked elsewhere with the periodic table.
Lutetium looks like “a good candidate to try,” Dias said.
It has 14 electrons localized in its f-orbital configuration that softens the phonon (a quantum of acoustic energy) and enhances the electron-phonon coupling necessary for superconductivity at ambient temperature.
“The key question was, how are we going to stabilize it to reduce the required pressure? And that’s where nitrogen came into the picture,” Dias said.
According to Dias, nitrogen, like carbon, has a rigid atomic structure that can be used to create a more stable, cage-like lattice within a material and that stiffens low-frequency optical phonons.
This structure provides stability for superconductivity to occur at low pressure, the study said.
Dias’ team created a gas mixture of 99 percent hydrogen and one percent nitrogen, placed it in a reaction chamber with a pure sample of lutetium, and allowed the components to react at 392 degrees Fahrenheit, or 200 degrees Celsius, for two to three days. .
The resulting lutetium-nitrogen-hydrogen compound initially had a “bright blue color,” the paper explains.
The study said that when the compound was compressed in a diamond anvil cell, a “startling visual change” occurred: from blue to pink at the onset of superconductivity and then to a bright red non-superconducting metallic state.
“It was very bright red,” Dias said. “I was shocked to see colors of this intensity. We humorously suggested a code name for the material in this position – ‘radimatter’ – after the material that Spock created in the popular 2009 Star Trek film.” Code name stuck.
The 145,000 psi pressure required to induce superconductivity is about two orders of magnitude lower than previous low pressures created in Dias’s laboratory.
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