Superconductivity sounds like a new Marvel hero, but it’s really something even cooler.
Several articles are currently doing the rounds about a mysterious material LK-99. Supposedly, it’s a superconductor at room temperature, which would be a huge discovery. What’s that about?
Conductivity is the scientific term for how well a certain material can conduct electricity. Electrical current is what we call charged particles (like electrons or ions) carrying an electrical charge from one place to another.
We use electrical currents every day, of course. When you plug your phone charger into a power socket, a current starts to flow from one of the socket’s connectors to the other. The current carries energy, and the charger you plugged in transfers most of that energy to your phone battery, and a little to heat (chargers get warm). The phone later converts part of that energy to light (on your phone display), motion (the speaker on your phone), and heat (phones get warm).
Carrying a current from point A to B is usually done through cables made of copper. There are copper wires in your phone’s charger cable, and behind the socket in your wall, and in the ground running to your house.
You can move energy around in other ways. For example, with a large enough potential difference, you can send it through the air — we see this often in lightning storms. You can also send energy places using lasers (like from orbit). However, in practice, using copper cables to transfer energy is the most economically and energy efficient method. At the moment, at least.
So what’s special about copper?
Conductivity in the period table
Copper has a lot of what we call free electrons. Each element in the period table has a number of electrons. You might think ‘more electrons conducts better’, but that’s not how it works.
Electrons circle the atomic nucleus in various configurations, with electrons grouped in shells around the atom. Depending on the configuration of those shells, some electrons in the outer shell can move around more freely. Because conductivity requires electrons to move energy from A to B through a material, more free electrons equals better conductivity.
Electron configurations are similar along columns of the period table, so the most conductive elements are all in the same column: twelve. Why that column has the most free electrons is beyond this simple blog post, but trust me — or rather, trust science. That column has copper (Cu), silver (Ag), gold (Au), and roentgenium (Rg). And guess what, copper is not the most conductive.
Why not silver?
The most conductive element we know is actually silver, then copper, then gold. Roentgenium is probably conductive, but it’s too high on the period table to make enough for testing, and what we can make falls apart quickly. We’re not going to make cables out of it any time soon.
Anyway, silver is a better conductor than copper, but it is way more expensive. It also has another downside that anybody with silver spoons knows: it oxidizes rapidly. And guess what, oxidized silver does not conduct current very well. Copper also oxidizes, and turns green, but slower. Gold is the least reactive, but also the least conductive and most expensive.
So, copper works best. It’s relatively cheap, and you can put it in protective coating to prevent oxidizing. For connectors at the end of the cable, which are open to air, you can use alternative metals. Audiophiles often prefer gold connectors, and you can now see why. It actually doesn’t effect digital audio, only analog, and encoding matters more these days, but there it is.
Okay, silver is the best conductor, but copper is more useful. So, we’re done, right?
Wrong. There are other factors that can lead a material to be more conductive, namely pressure and temperature. When you cool a metal, its conductivity increases gradually, all the way down to absolute zero. So electrical resistance is temperature-dependent. Silver, for example, has an electrical resistance of 1.59 x 10-8 Ωm at room temperature (20 degrees celsius). This resistance goes down as it approaches absolute zero temperature, but it stays shy of actual zero. In other words, if you send a current through, some energy will be converted to heat along the way, even at 0 Kelvin.
However, some materials behave differently. Their conductivity decreases, but then, below a certain temperature, their electrical resistance suddenly becomes 0. That means no energy is lost to heat or light when you push a current through. That’s what’s called superconductivity.
Imagine a superconductive cable. It would have no loss of energy at all. You could send massive amounts of energy through cables across a continent, and there would be no heat, or energy loss. Your charger wouldn’t grow hot.
Because magnetism and electrical currents can interact, a superconductor also some special magnetic properties. Below the superconductive temperature, it ejects magnetic fields. This is called the Meissner effect. It can make the material hover over a magnet. Imagine what that could do for maglev trains.
Superconductors have other uses. Because of their low electrical resistance, they would be able to achieve high communication speeds, similar to fiber, because they don’t heat up.
Finally, certain medical applications, like MRI scanners would benefit from superconductors.
So what about this new miracle material? Why is it a big deal? And is it true?
So far, we’ve only found superconducting materials that operate at very low temperatures. And while that is good for scientific experiments, we can’t supercool a hundred kilometers of cable. In other words, you need a room-temperature superconductor for that.
Scientists did manage to produce a superconductor at 15 degrees celsius, carbonaceous sulfur hydride. There is a catch. It has to be at a pressure of 267 GPa, which is ridiculously high — a few million times the atmospheric pressure at ground level on earth. So, yeah, that’s not going to work either.
Enter LK-99: a normal pressure, room-temperature superconductor. Supposedly.
Given the scientific community has found no materials that come even remotely close to the properties LK-99 offers, they are understandably skeptical. If it’s real, and economically producable, it could change the world. But is that likely? No, not really. There’s a good chance mistakes were made.
It’s similar to cold fusion, a break-through that would also change the world, and no claims have held up over the years. But who knows.
Economically viable superconductivity at room temperature would be awesome. It would change our electrical grids forever, and probably our internet as well. But, yeah, let’s see if it pans out first. History teaches us to be skeptical.
I guess we’ll see.