Researchers at the School of Engineering and Applied Science have taken a major step toward reaching one of the most sought-after goals in physics: room temperature superconductivity.
Superconductivity is the lack of electrical resistance and is observed in many materials when they are cooled below a critical temperature. Until now, superconducting materials were thought to have to cool to very low temperatures (minus 180 degrees Celsius or minus 292 degrees Fahrenheit), which limited their application.
Since electrical resistance makes a system inefficient, eliminating some of this resistance by utilizing room temperature superconductors would allow for more efficient generation and use of electricity, enhanced energy transmission around the world and more powerful computing systems.
“Superconductivity is perhaps one of the last great frontiers of scientific discovery that can transcend to everyday technological applications,” said Maddury Somayazulu, a SEAS associate research professor. “Room temperature superconductivity has been the proverbial 'holy grail' waiting to be found, and achieving it...is a paradigm-changing moment in the history of science.”
The key to this discovery was the creation of a metallic, hydrogen-rich compound at very high pressures. The researchers used diamond anvil cells, devices used to create high pressures, to squeeze together miniscule samples of lanthanum and hydrogen. They then heated the samples and observed major changes in structure. This resulted in a new structure, LaH10, which the researchers previously predicted would be a superconductor at high temperatures.
While keeping the sample at high pressures, the team observed reproducible change in electrical properties. They measured significant drops in resistivity when the sample cooled below -13 degrees Celsius or 8 degrees Fahrenheit at 180-200 gigapascals of pressure, presenting evidence of superconductivity at near-room temperature.(A pascal is a unit of measure for pressure.)
In subsequent experiments, the researchers saw the transition occurring at even higher temperatures, up to 44.33 degrees Fahrenheit. Throughout the experiments, the researchers also used X-ray diffraction to observe the same phenomenon. This was done through a synchrotron beamline of the Advanced Photon Source at Argonne National Laboratory in Argonne, Ill.
“We believe this is the beginning of a new era of superconductivity,” said Russell Hemley, a SEAS research professor. “We are confident many other hydrides—or superhydrides—will be found with even higher transition temperatures under pressure.”
Hydrides are compounds where one hydrogen atom is combined with another element. Superhydrides are hydrides with an extremely high hydrogen content, which are supposed to transition at higher temperatures, making them ideal to use in experiments.
Along with Dr. Somayazulu and Dr. Hemley, the research team included Muhtar Ahart, a SEAS associate research professor, and collaborators at the Carnegie Institution of Washington and Argonne National Laboratory. They currently are working to add experimental capabilities on the beamline at the Advanced Photon Source and elsewhere to be able to quantify the critical parameters of this class of superconductors. In the future, the team hopes to develop a deeper understanding of the underlying physics of superconductors in order to understand its numerous practical applications.
The study was published Monday in the journal Physical Review Letters.