Superconductors are the secret sauce that many designs for quantum computers, particle accelerators, and fusion reactors depend on to function. But most superconductors need to be kept at ultra cold temperatures, a drawback that severely limits their use.
Now for the first time, researchers have created a material that acts as a superconductor at nearly room temperature. Unfortunately, there’s still a catch.
Superconductors are aptly named; they’re materials that conduct electricity with zero resistance, meaning a current can move through the material without losing any energy. They also expel magnetic fields thanks to a phenomenon called the Meissner effect.
If an external magnetic field is weak enough, it cannot penetrate the material, but stronger magnetic fields interact with superconductors in one of two ways, depending on the kind of superconductor.
Type-I materials fall out of their superconducting state if an applied magnetic field is strong enough, but Type-II superconductors allow applied magnetic fields to pass through them while still maintaining 0 electrical resistance.
Type-II materials are what make super strong electromagnets possible, like the kind that steer particles through the 27 kilometer loop of the Large Hadron Collider.
Normal magnets wouldn’t be able to guide the particles around tight turns, so without superconducting magnets the collider would have to be over 90 kilometers longer to reach the same energy level.
All of this amazing potential is unleashed only when superconductors are cooled below a critical temperature. For the Large Hadron Collider’s main magnets, that temperature is -271 degrees Celsius, almost 2 degrees above absolute zero.
Quantum computers like this one made by IBM have to keep their handful of quantum bits even colder, just 0.015 Kelvin. These extreme temperatures present extreme problems.
When the LHC started its multi-year planned upgrade in 2018, bringing the machine up to room temperature. Useful quantum computers with millions of physical quantum bits are currently beyond our reach because no one has made a practical method to scale up the cooling.
For all these reasons, a room temperature superconductor is considered the holy grail of condensed matter physics. And we’ve been slowly marching up the thermometer for some time now.
The first superconductor discovered in 1911 was mercury wire chilled to 4.2 Kelvin. By the 80s, scientists had found materials with a critical temperature of 30 Kelvin, and by the mid 90s they had gotten it up to a balmy 164 K, or about -109 degrees Celsius.
It took until 2015 to prove an idea from 1968 that stated hydrogen could act as a superconductor above room temperature if it was under enough pressure. To pre-compress the hydrogen, researchers combined it with sulfur, then squeezed the molecule between the tips of two diamonds to achieve a pressure of 155 gigapascals, more than a million times the atmospheric pressure you and I are experiencing right now. The material still had to be kept at 203 Kelvin, but we were getting warmer.
Finally, this year one experiment has turned up the heat and the pressure. Researchers started with a mixture of carbon and sulfur in between the diamonds of their vise. Next they piped in the gases hydrogen, hydrogen sulfide, and methane.
When the ingredients were hit with a laser, they reacted to form clear crystals. Then they cranked up the pressure. At 148 gigapascals, the crystals became superconductors at 147 Kelvin. The researchers ratcheted up the pressure even higher, to 267 gigapascals, and found the material had the properties of a superconductor at 287 Kelvin.
Heck, at this point we can just switch back to Celsius, that’s almost 14 degrees baby! Room temperature! Well sort of, more like a really chilly room. But still, that’s incredible progress.
Just because we’ve made these materials in a lab doesn’t mean they’re useful just yet. Remember those superconductors developed in the 80s and 90s? They work at relatively higher temperatures than those in the Large Hadron Collider, yet the accelerator doesn’t use them. That’s because so-called “high temperature” superconductors are difficult to manufacture in usable amounts.
One very recent proposal for a fusion reactor, MIT’s SPARC, could be a huge breakthrough in the field and it’s only possible because these materials are just becoming viable for large scale use. In its current state, the superconducting crystals the researchers made in their diamond vise don’t really have a practical application.
The researchers’ ultimate goal is to create a material that keeps its properties even when the pressure is released, and they’re not quite sure yet how to get there from here. When a usable room temperature superconductor finally becomes a reality it’ll be a game changer that will likely have a huge impact on our daily lives, but until then I wouldn’t go near a superconductor without a lot of layers on.
To learn more about why high temperature superconductors might make fusion power possible, check out an article on MIT’s proposed SPARC reactor.