Ever return home after a long journey from home only to wrinkle your nose in disgust at the ungodly smells emanating from your refrigerator, like a mild breeze from some future imperfect junk world? You probably already know that such acrid smells are the tail end of a chemical reaction your food undergoes when left to the atmosphere. You may even know that the cause behind one of the worst smells–rotten eggs–is actually a chemical called hydrogen sulfide.
THIS ROTTEN SMELL IS SIGN OF A SUPERCONDUCTOR
But recently a pair of physicists in Germany have just proved that hydrogen sulfide becomes a superconductor at record high temperatures. In its solid form, the compound chemical is capable of conducting electricity sans resistance at 203.5 K. This is still roughly 70°C below water’s freezing point. But it still stands that this is a higher temperature than we’ve ever brought the compound, and what’s more, this is the closest anyone has come to creating superconductivity at room temperature.
SUPERCONDUCTORS AND TRAINS
If we can create superconductors at room temperature, then there’s a chance to apply this technology to magnetically levitated trains. The real challenge, though, is the fact that hydrogen sulfide becomes a superconductor only at more than 100 million times atmospheric pressure, which is about one-third as great as the pressure in Earth’s core. Unfortunately, there doesn’t seem to be a way of broadening this new superconductor’s applications.
“Where does it go from here?” asks Igor Mazin, a theorist at the U.S. Naval Research Laboratory in Washington, D.C. “Probably nowhere.” But even if we can’t have rotten-egg-levitated-trains, our understanding of superconductivity itself is changing, growing into another field.
BRIEF EXPLANATION OF SUPERCONDUCTORS
Scientists already know of several types of superconductivity. It’s nothing new. The most ordinary type, involving a metal like niobium, carries electricity sans resistance only when its cooled to almost absolute zero, i.e. 0 K. This metal is composed of a cage-like assemblage of positively charged ions which conduct negatively charged electrons as they flow through the metal’s structure. Usually, electrons lose their energy as they’re deflected off of quivering ions, but, if the temperature is low enough, electrons pair up, and, since the pair must be broken to be deflected, and their energy at low temps is scarce, the pair of electrons flow without hindrance through the substance.
GOOD VIBRATIONS STICK TOGETHER
But in order for the pair of electrons to stick together, a series of vibrations of the ion lattice known as a phonon is required. Phonons have difficulty holding together at higher temps, and the record temperature for such an ordinary superconductor was 39 K (i.e. -234.5°C), and only with the help of magnesium diboride.
But in the 1980s physicists found a family of “high-temperature superconductors,” which are complex compounds composed of copper and oxygen–two elements capable of becoming superconductors at much higher temperatures. Ten years ago, scientists found an analogous family of iron and arsenic compounds. In these materials, electrons’ interactions alone are sufficient to cause the glue-like effect. The mystery is how it is this happens.
NEW RECORD FOR SUPERCONDUCTORS
The new record for high temp superconductivity was set by Alexander Drozdov and Mikhail Eremets, both of whom are physicists at the Max Planck Institute for Chemistry in Mainz, Germany. Their sample of hydrogen sulfide was a miniscule disc, less than the diameter of a human hair, and, after being squeezed at one-third the pressure of Earth’s core, they saw electrical resistance vanish at 190 K.
Before the two gave their squeeze, the record was 164 K from a copper-and-oxygen superconductor, which required 350,000 times atmospheric pressure. Naturally, when Drozdov and Eremets came forward with claims of a superconductor at higher temps with such low pressure, many scientists were skeptical.
VERIFYING FINDINGS
To put their doubts to rest, the two physicists demonstrated the second sign of superconductivity, which is the negation of an externally applied magnetic field by the superconductor’s own, internally generated field. As they predicted, the superconductor did create a dead-zone within the external field, where its own field persisted, sans resistance.
Although many scientists predict that scientific research will move beyond the pursuit of superconductors which persist in room temp and pressure, the effect of this progress on the entirety of electrical technology is fascinating in its own right.
