Water With Superconducting Properties When Doped

Superconductivity is a topic talked about often and it is no surprise to see why. Being able to create wires that have literally no resistance to the current flowing through them is an absolutely insane idea. The most recent major discoveries made in the superconducting field was that metal hydrides could be made into superconductors when they were placed under high pressure. The current record for the highest critical temperature is in trihydrogen sulphide (H3S) which became superconducting at 203K provided the conditions were at 200 gigaPascal of pressure.

The interaction between the conducting electrons and the lattice phonons is the producer of superconductivity and it seems that hydrogen is a component that assists in this effect. Many hydrides have been looked into in the hope of finding a high temperature superconductor such as phosphine (P2H4), hydrogen selenide (H2Se) and silane (SiH4). The problem arises in that these compounds only transition into metals when put under the already mentioned extreme pressures. Any possible metallic phases at lower temperatures are often too unstable for even experiments to be done and so far too unstable for practical use.

One suggestion that these extreme phase changes may be useful if the correct doping can be applied. Doping, the addition of impurities that provide extra electrons (or sometimes lack of electrons known as holes), can be used to convert semiconductors into conductors. In 2004 it was shown that diamond when doped with boron could be induced to superconductivity along with some other examples. These cases still had low critical temperatures of only a few Kelvin above absolute zero but there is still a lot of potential for this method. Recently work was performed to see if a combination of doping and high pressure could cause a high temperature superconducting transition in a hydride. The hydride that was selected is the most common, oxygen hydride, in other words water (H2O). The work was with a number of different doping agents with only nitrogen showing any success at creating a stable structure with a series of holes present for conducting. Without doping it is estimated that water would only become a metal at over 5 teraPascal, an extremely large pressure. With the nitrogen present, however, it was predicted that the superconducting phase could begin in water at 60K with pressures of 150 gigaPascal. Hopefully superconductivity can be studied further in these systems with further hydrides becoming pressure doped.

Paper links: Emergence of superconductivity in doped H2O ice at high pressure


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