The science of superconductivity has just made a new achievement: for the first time, physicists have allowed an electric current to flow freely in a circuit without resistance – we achieve superconductivity at room temperature, about 15 degrees C.
The results of this study broke the previously set record, achieving superconductivity at -23 degrees Celsius. The dramatically narrowed temperature gap makes us excited about a no-resistance future.
“Because of the impediment of low temperatures, many materials with great properties cannot change the world as we envision them. However, our discovery will break that barrier, opening the door to potential applications.“, Physicist Ranga Dias from the University of Rochester said in the press release.
In 1911, humanity for the first time discovered superconductivity. That was also the beginning of the journey to find practical applications of superconductors in material science.
To achieve superconductivity, a material must have two factors.
First, the resistance must be zero. Normally, electric current will always have trouble moving in any conductive matter – just like the way we ride in a car that’s blocked by the wind. The higher the conductivity of the material, the lower the resistance, the more comfortable it will be to move electricity.
The second element is the “Meissner effect”, which talks about the properties of the magnetic fields emitted by superconducting materials. One can imagine the shape of this magnetic field by placing a permanent magnet on top of the superconducting material, which causes the magnet to float in the air.
An example of the Meissner effect.
Also from 1911 up to now, we have deduced many applications of superconductivity. From maglev soaring in the wind, the ability to transmit information lossless to large power grids. But all of the above examples are still concepts on paper, because superconductivity is not easily achieved.
Typically, superconducting materials are created and kept in an extremely low temperature environment, much lower than ambient. Superconducting materials are very expensive to store, so they cannot be applied in everyday life.
Physicists have recently been successful in increasing the temperature of light elements such as hydrogen sulfide and lanthanum hydrite. In the gaseous form, hydrogen is an insulator, and we have to metal it under extreme pressure to create superconductivity.
“To get superconducting at high temperatures, you will need light elements that have strong bonds. Here are two must-have standards. Hydrogen is the lightest material, and they possess one of the strongest chemical bonds“, Physicist Dias said.
“Solid metal hydrogen is, in theory, believed to have a high Debye * temperature and strong electron-phonon ** pairings that are essential to achieving superconductivity at room temperature.“.
(**): Phonons are stimuli of an ordered array of atoms and molecules in solid matter, mainly solid matter and some liquid matter. The phonon can also be considered as a quantized sound wave, just as the photon is the quantization of the light wave.
Scientists assume that metallic hydrogen does exist in the Earth’s core, where the pressure is extremely high.
Only pure metallic hydrogen can be made with extreme pressure, and the conditions for creating this material are difficult to achieve. In recent years, only two research groups claim to have done the impossible.
In 2017, physicists said that they produced metallic hydrogen at a pressure between 465-495 gigapascals and at a temperature of 5.5 Kelvin, which is -267.65 degrees Celsius. In 2019, a team of researchers Another study reported the results of generating metallic hydrogen at a pressure of 425 gigapascals and 80 kelvin, which is -193 degrees Celsius. However, neither of the two materials above survived at room temperature.
We still have materials as effective as metallic hydrogen, hydrogen sulfide and lantan hydrite, two hydrogen-rich metals. They can be superconducting like pure metallic hydrogen at a much lower pressure level.
So, a group of physicists led by Elliot Snider from the University of Rochester set out to test these materials. First, they combined hydrogen with yttrium to create super hydrite yttrium. This material exhibited superconductivity at a temperature of -11 degrees Celsius and a pressure level of 180 gigapascals.
The team then combined carbon, sulfide, and hydrogen to form carbon-based hydrite sulfide. They inserted this material into the diamond anvil (a tool that can create enormous pressure using two diamond components to squeeze the matter in between) to measure superconductivity. The results were surprising: the new material achieved superconductivity at 270 gigapascals and 15 degrees Celsius.
Close-up of diamond anvil.
Obviously, this superconducting material still cannot be used in everyday life. The amount of superconducting material for the experiment is extremely small, and the pressure level of 270 gigapascals is still not ideal.
The next step, the team will try to reduce the amount of pressure required to create superconductivity, through modifying the chemical makeup of the sample. If “concoction” is successful to produce an effective superconducting material, scientists believe that superconducting at room temperature, with moderate pressure, will be within reach of humanity.
The new research has been posted on Nature.