Superconductive materials could revolutionize electronics – if only they weren’t so fussy.
Coaxing materials into this state, where electrical currents flow freely with no resistance at all, requires either extremely low temperatures or extremely high pressures, or both.
That means that any advantages you could get in the real world – such as electric vehicles that recharge instantaneously – would be offset by needing to pack a cryogenic freezer or a diamond anvil cell in your back seat.
But now, scientists are one step closer to making superconductive materials that operate near everyday temperatures and pressures.
A team led by physicists at the University of Houston has just set a new world record for superconductivity, achieving the highest temperature under ambient pressure.
That temperature might not sound very high – a brisk -122.15 degrees Celsius (-187.87 degrees Fahrenheit) – but it’s positively sweltering compared to the usual requirement of just a hair above absolute zero (-273.15 degrees Celsius).
The new record also helps to break a decades-long stalemate in superconductor research.
“This is a major step toward practical superconductors that operate at room temperature and pressure,” says Hua Zhou, a physicist at Argonne National Laboratory in the United States.
“With this material still superconducting at normal pressure, scientists can study it with widely available instruments and begin developing technologies that work under everyday conditions.”
The material in question is what’s called a cuprate superconductor, which is made up of layers of copper oxide interspersed with other metal oxides. In this case, that’s mercury, barium, and calcium.
This particular formulation is known as Hg1223, and since 1993 it’s held the record for highest-temperature superconductor under ambient pressure. That record was a not-so-balmy -140.15 degrees Celsius.
To improve that figure, the researchers on the new study performed a protocol known as pressure-quenching on the material. First, Hg1223 was compressed in a diamond anvil cell at up to 30 gigapascals of pressure. That’s almost 300,000 times higher pressure than what we’re subjected to at sea level.
But the squeeze was only temporary. That pressure was then released very quickly, which causes the material to become metastable – a state that preserves some of its quantum weirdness without needing to maintain the extreme pressure.
One of the best-known examples of a metastable material might be on your hand right now.
Diamonds are little more than carbon that’s been exposed to extreme pressure deep inside Earth, but they maintain their new structure even after they’re hauled to the surface.
When materials are subjected to high pressures, it literally squeezes the atoms closer together to form new arrangements. Releasing the pressure slowly lets the atoms relax back into their normal structure – but a quick release triggers the formation of small defects in the material.
And it’s these defects that seem to keep Hg1223 superconductive at higher temperatures, even when pressure returns to ambient levels.
The material’s superpowers were confirmed by analysis with the Advanced Photon Source (APS), a powerful X-ray laser at Argonne that can precisely monitor microscopic variations in a material.
Hg1223 isn’t the warmest superconductor ever made: That honor goes to a sample of lanthanum decahydride, which remained superconductive all the way up to -13.15 degrees Celsius, a temperature you could reach in your freezer at home.
What you can’t achieve at home, however, is the crushing pressures of 190 Gigapascals, comparable to Earth’s outer core. It’s a trade-off that makes Hg1223’s 30 Gigapascals look calm and cruisey.
Related: Physicists Discover Superconducting States That Get Stronger Under Conditions Meant to Kill Them
But the long-term hope is that eventually, there might not need to be a trade-off at all. Room-temperature, ambient-pressure superconductivity could have massive benefits to grid-scale energy storage and delivery, electric vehicles, and even levitation.
Those applications are still a long way off, of course, but each new step gets us a little closer.
The research was published in the journal Proceedings of the National Academy of Sciences.
This article was fact-checked by Carly Cassella and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
