By Josh Perry, Editor
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An international team of scientists from the University of Chicago (Ill.) and the Max Planck Institute in Germany, using technology from Argonne National Laboratory, observed superconductivity in lanthanum superhydrides at higher temperatures than previously recorded.

Scientists bombarded a sample of a new superconducting material (center) with X-rays to study its structure at the Advanced Photon Source. (Drozdov et al/University of Chicago)

According to a report from the university, superconductivity was seen at -23°C, which was about 50 degrees higher than the previous record.

While extremely high pressure (between 150-170 gigapascals) was required to achieve superconductivity in a sample that was only a few microns across, scientists believe this is another step towards attaining superconductors that work at room temperatures.

“In fact, the material showed three of the four characteristics needed to prove superconductivity: It dropped its electrical resistance, decreased its critical temperature under an external magnetic field and showed a temperature change when some elements were replaced with different isotopes,” the article explained. “The fourth characteristic, called the Meissner effect, in which the material expels any magnetic field, was not detected. That’s because the material is so small that this effect could not be observed, researchers said.”

Researchers used the Advanced Photon Source at Argonne Lab to study the structure and composition of the material, which was squeezed between two diamonds to achieve the necessary pressure.

“Because the temperatures used to conduct the experiment is within the normal range of many places in the world, that makes the ultimate goal of room temperature—or at least 0 degrees Celsius—seem within reach,” the article concluded.

The research was recently published in Nature. The abstract read:

“With the discovery of superconductivity at 203 kelvin in H₃S, attention returned to conventional superconductors with properties that can be described by the Bardeen–Cooper–Schrieffer and the Migdal–Eliashberg theories.

“Although these theories predict the possibility of room-temperature superconductivity in metals that have certain favorable properties—such as lattice vibrations at high frequencies—they are not sufficient to guide the design or predict the properties of new superconducting materials. First-principles calculations based on density functional theory have enabled such predictions, and have suggested a new family of superconducting hydrides that possess a clathrate-like structure in which the host atom (calcium, yttrium, lanthanum) is at the center of a cage formed by hydrogen atoms.

“For LaH₁₀ and YH₁₀, the onset of superconductivity is predicted to occur at critical temperatures between 240 and 320 kelvin at megabar pressures. Here we report superconductivity with a critical temperature of around 250 kelvin within the Fm3¯mFm3¯m structure of LaH₁₀at a pressure of about 170 gigapascals.

“This is, to our knowledge, the highest critical temperature that has been confirmed so far in a superconducting material. Superconductivity was evidenced by the observation of zero resistance, an isotope effect, and a decrease in critical temperature under an external magnetic field, which suggested an upper critical magnetic field of about 136 tesla at zero temperature.

“The increase of around 50 kelvin compared with the previous highest critical temperature is an encouraging step towards the goal of achieving room-temperature superconductivity in the near future.”