The news doesn’t go long without some kind of superconductor announcement these days. Unfortunately, these come in several categories: materials that require warmer temperatures than previous materials but still require cryogenic cooling, materials that require very high pressures, or materials that, on closer examination, aren’t really superconductors. But it is clear the holy grail is a superconducting material that works at reasonable temperatures in ambient temperature. Most people call that a room-temperature superconductor, but the reality is you really want an “ordinary temperature and pressure superconductor,” but that’s a mouthful.
In the Hackaday bunker, we’ve been kicking around what we will do when the day comes that someone nails it. It isn’t like we have a bunch of unfinished projects that we need superconductors to complete. Other than making it easier to float magnets, what are we going to do with a room-temperature superconductor?
We draw schematics as though wires have no resistance. But in real life, that’s not true. Electrons flowing through a wire will cause some loss. However, in 1911, a Dutch physicist, Heike Kamerlingh Onnes, pioneered low-temperature research. At the time, common wisdom observed that while lowering a metal’s temperature reduced resistance, it was likely that at absolute zero, electrons would be immobile and, thus, no electrical current would flow at that temperature. Onnes, observed quite the opposite. Starting with mercury, he observed that at 4.2 K, very near absolute zero, the resistivity of the material abruptly went to zero.
Of course, getting materials near 4.2 K is a big problem. For example, liquid nitrogen — which is usually used in labs when you want something cold — boils at 77 K. Even then, cooling things with liquid nitrogen isn’t very practical for most applications. However, there are some ceramic materials that exhibit superconductivity above 90 K so it is possible to use superconductors today if you are willing to cool with something like liquid nitrogen.
Superconductors don’t exhibit electrical loss, so a current can travel forever in a loop of superconducting material. Experiments have observed currents traveling in a loop for nearly three decades with no measurable loss, and the ories predict currents would sustain at least 100,000 years if not more than the lifetime of the universe.
The physics behind it all is hairy. In normal conductors, electrons flow across an ionic lattice. Some electrons collide with the ions, converting some of their energy to heat. In a superconductor, the electrons bind in weak pairs known as Cooper pairs. The pairs form a type of superfluid that can flow without energy dissipation. You can see a more detailed explainer in the video below.
One important takeaway about superconductivity is that it disappears above given current and magnetic field levels. So in addition to characterizing superconductors by their critical temperature and pressure, it’s also important to know the critical current density and critical magnetic field strengths.
There are several places where superconductors are used today: SQUID (superconducting quantum interference devices) are very sensitive magnetometers that use Josephson junctions, superconductors with a thin insulating component. These are common in labs, MRI machines, and quantum computers. It is possible to use them to locate submarines, too. They do not need to pass large currents and are not subject to strong fields. Presumably, if you had room-temperature superconductors, you could form Josephson junctions with them, and all of these devices would become less expensive and easier to operate.
Another place we see superconductors already is in electromagnets for things like MRIs, particle accelerators, levitating trains, and fusion reactors. These are the applications that require high current or are subject to strong magnetic fields. Today, these applications all require liquid nitrogen or liquid helium. If future room-temperature superconductors end up having high critical current densities as well, you could cheaply build very strong electromagnets.
Certainly, places where we use cold superconductors today would just get better. But there are also several new applications that you could do today but the cooling overhead is too prohibitive. Of course, some of it will depend on the characteristics of the unknown magic material. For example, you often hear people say that electrical transmission lines could be superconductors. That’s true, but only if they have high critical magnetic field parameters, because otherwise they don’t really work for AC current. On the other hand, we use AC partly as a hedge against losses, so if you were willing to change the whole system, you could possibly use superconducting cables to transmit lower DC voltages long distances, but then you’re relying on a high critical current density.
We aren’t entirely certain what superconductors will do for consumer electronics. Better magnets might mean better motors, so maybe your electric drill will be lighter and more powerful. Lower resistance in components could mean less heat loss and higher battery life. You often hear that superconductors will lead to phones that last weeks on a charge. Maybe, but our guess is not right away. We doubt that the loss in interconnect is really what’s draining your phone battery. However, it is true that components that have fewer inefficiencies could lead to longer battery life. It might allow faster charging, too. After all, GaN charging is more efficient because it produces less heat than conventional electronics. A superconducting charger would be even faster.
In general, you could expect warm superconducting electronics to be able to handle more current in smaller spaces. There is some thought they may also be faster. Eary Josephson junctions (admittedly, in liquid helium) were much faster than conventional transistors in use at the time. Of course, transistors are better today, but presumably widespread use of superconducting junctions would also bring improvements.
What Will You Do?
The truth is, though, since we don’t know the properties of the room-temperature superconductor, we don’t know what it may or may not bring. Maybe you won’t have a superconducting cell phone because it would reset itself whenever you encountered a magnetic field. We simply don’t know.
However, we did want to ask. If you could open your web browser and order superconducting parts right now, what would you do with them? Do you want wire? Coils? Switching devices? And why? Let us know in the comments below.
If you have access to liquid nitrogen, maybe you are already using superconducting material. If so, let us know that, too. Or, perhaps you are working on making the next material to claim room-temperature superconductivity.
Featured Image: The eight toroidal superconducting magnets at the heart of the LHC, credit: CERN. […]