Superconductivity of Tellurium Polyhydride with Tc above 90K

For decades, scientists have been hunting for a material that can conduct electricity without any loss of energy, a state known as superconductivity. While this phenomenon is well-known, it usually requires temperatures so cold that they are only found in the deepest reaches of space, making practical use incredibly difficult. The search has recently intensified around a specific family of materials called polyhydrides, which are compounds made of hydrogen bonded to other elements. Theoretically, these materials hold a unique promise: if you squeeze them with enough pressure, the hydrogen atoms are forced so close together that they begin to behave like a metal, potentially allowing electricity to flow freely at much warmer temperatures than ever before. This concept of "pre-compression" suggests that by applying immense force, researchers could lower the temperature needed for superconductivity to a point where it might one day be useful in the real world.

Building on this idea, a team of researchers has now added a new chapter to the story by discovering superconductivity in a compound made of tellurium and hydrogen. Tellurium is a chemical element found on the right side of the periodic table, and when combined with hydrogen under extreme conditions, it forms a material that conducts electricity without resistance at a temperature of about 91 Kelvin, which is roughly -182 degrees Celsius. While this is still far below the freezing point of water, it is a significant leap forward for this specific type of material and marks the first time superconductivity has been observed in a hydrogen-rich compound of tellurium.

To create this material, the scientists had to recreate the crushing pressures found deep within the Earth's core. They used a device called a diamond anvil cell, which consists of two tiny diamonds with flat tips that can be pressed together to squeeze a sample between them. Inside this microscopic chamber, they placed a speck of tellurium and a hydrogen-rich substance called ammonia borane, which served as both the source of hydrogen and the medium to transmit pressure. By heating the sample with a powerful laser to temperatures around 2,000 Kelvin, they broke down the ammonia borane, releasing hydrogen gas that reacted with the tellurium to form the new compound. This process was delicate and difficult; the intense heat required to forge the material often damaged the diamond anvils, making it hard to repeat the experiment or test the material under changing pressures.

Once the material was formed, the researchers measured its electrical resistance while keeping it under high pressure and cooling it down. They observed that as the temperature dropped, the electrical resistance of the sample fell sharply and eventually vanished completely, a clear sign that the material had become a superconductor. In one of their samples, this zero-resistance state appeared at a temperature of about 91 Kelvin. To confirm that this was indeed superconductivity and not just a change in the material's structure or magnetism, they applied magnetic fields. They found that as the magnetic field grew stronger, the temperature at which the material became superconducting dropped lower, a behavior that is a hallmark of true superconductors. This sensitivity to magnetic fields also suggested that the superconducting regions within the sample were connected by weak links, a common feature in materials made of many tiny crystals.

The team then turned to a powerful X-ray beam at a large research facility to look inside the material and see how its atoms were arranged. The diffraction pattern they captured revealed that the superconducting phase was a specific compound called TeH4, where one atom of tellurium is bonded to four atoms of hydrogen. The structure of this compound is quite distinct, featuring cages of hydrogen atoms that share faces with one another, forming a lattice that resembles a honeycomb. Within this structure, pairs of hydrogen atoms sit close together, acting almost like individual molecules trapped inside the larger framework. This arrangement matches theoretical predictions made by other scientists, who had suggested that this specific shape would be stable under such high pressures and capable of superconductivity.

The discovery places tellurium polyhydride alongside sulfur hydride as one of the few known chalcogen polyhydride superconductors. While the researchers could not cycle the pressure up and down to see how the material behaved over a wider range due to the fragility of their samples, the data they collected provides a solid foundation for understanding how hydrogen-rich materials behave under extreme stress. The findings confirm that by squeezing these elements together, it is possible to create new states of matter that conduct electricity with perfect efficiency at temperatures that, while still very cold, are warmer than those required by traditional superconductors. This work expands the map of known superconducting materials and offers further evidence that the theoretical promise of high-temperature superconductivity in polyhydrides is becoming a tangible reality.