Superconductors are the ideal electrical conductors, having the desirable attribute of no electrical resistance allowing 100% efficiency for power transmitted along them. Current applications of superconductors are limited to areas where their operational complexity (most of which comes from the cooling required to keep them in a superconducting state) is outweighed by the benefits they provide. Such complexity is what has driven the search for a superconductor that can operate at normal temperatures as they would bring about a whole new swath of applications that are currently not feasible. Whilst we’re still a long way from that goal a new temperature record has been set for superconductivity: a positively balmy -70°C.
The record comes out of the Naval Research Laboratory in Washington DC and was accomplished using hydrogen sulfide gas. Compared to other superconductors, which typically take the form of some exotic combination metals, using a gas sounds odd however what they did to the gas made it anything but your run of the mill rotten egg gas. You see to make the hydrogen sulfide superconducting they first subject the gas to extreme pressures, over 1.5 million times that of normal atmospheric pressures. This transforms the gas into its metallic form which they then proceeded to cool down to its supercritical temperature.
Such a novel discovery has spurred on other researchers to investigate the phenomena and the preliminary results that are coming out are promising. Most of the other labs which have sought to recreate the effect have confirmed at least one part of superconductivity, the fact that the highly pressurized hydrogen sulfide gas has no electrical resistance. Currently unconfirmed from other labs however is the other effect: the expulsion of all magnetic fields (called the Meissner effect). That’s likely due to this discovery still being relatively new so I’m sure confirmation of that effect is not far off.
Whilst this is most certainly a great discovery, one that has already spurred on new wave of research into high temperature superconductors, the practical implications of it are still a little unclear. Whilst the temperature is far more manageable than its traditional counterparts the fact that it requires extreme pressures may preclude it from being used. Indeed large pressurized systems present many risks that often require just as complex solutions to manage them as cryogenic systems do. In the end more research is required to ascertain the operating parameters of these superconductors and, should their benefits outweigh their complexity, then they will make their way into everyday use.
Despite that though it’s great to see progress being made in this area, especially one that has the potential to realise the long thought impossible dream of a room temperature semiconductor. The benefits of a such a technology are so wide reaching that it’s great to see so much focus on it which gives us hope that achieving that goal is just a matter of time. It might not be tomorrow, or the next decade, but the longest journeys begun with a single step, and what a step this is.
Superconductors are an incredible scientific discovery and not just because they have the oh-so-nice property of having 0 electrical resistance. They also have the peculiar property of ejecting all magnetic fields from within them, an interesting phenomena considering the duality of electromagnetism. Unfortunately traditional superconductors required extremely low temperatures to exist, usually not far off absolute zero. This made them impractical for the many uses we could think of for them as whilst the lack of resistance would prove a boon for power transmission the ongoing maintenance would prove to be far too costly. However recent materials advancements have given rise to what we call high temperature superconductors which has opened up many new avenues of research.
Don’t let their moniker fool you though, the temperatures that most of these operate at are still well below freezing, however they do become superconducting at temperatures that are achievable using coolants like liquid nitrogen rather than exotic solutions relying on cryogenic fluids like liquid helium. This has lead to a lot of research with these particular kinds of superconductors and interestingly some demonstrations that almost appear like magic when you first see them:
As I mentioned earlier superconductors expel all magnetic fields from within them, however when the superconductor is thin there will be little areas of weakness where the magnetic field can get through. Since the superconductor is trying its darnedest to expel those fields it locks them in those small areas allowing the superconductor to levitate on the field. The locking happens in the direction of the magnetic field which actually allows you to do some very interesting things (as demonstrated in this video). The effect only lasts as long as the cooling however and once that’s gone the levitation effect disappears instantly.
Really hammers home Arthur C. Clarke’s quote: “Any sufficiently advanced technology is indistinguishable from magic.” doesn’t it?