The electricity surging to your appliances, TV, and lights doesn’t have the smoothest
ride from its power source.
Some of the energy traveling through transmission lines,
typically made of aluminum or copper, is lost when electrons crash into atoms.
These losses wouldn’t happen if the wires were made of superconductors,
materials that conduct electricity without any resistance. The applications span beyond wires to powerful
magnets that can be used to levitate trains, and extremely energy-efficient computer chips.
There are many types of superconductors—most require frigid temperatures to operate,
which limits how easily they can be utilized.
But in October of 2020, after decades of searching,
researchers reported a superconductor that worked at about 14 degrees Celsius—
the temperature of a well-maintained wine cellar. This breakthrough came with a different caveat:
the superconductor required intense pressure to function—almost 3/4 of the pressure at the earth's center.
The first superconductors discovered in 1911
were elemental metals, such as mercury, cooled to just above absolute zero.
At that temperature, electrons no longer bump into atoms when they’re traveling.
The room-temperature superconductor was created by crushing carbon, sulfur, and hydrogen between
two diamond jaws, that eventually exploded. This resulted in a carbonaceous sulfur hydride,
one of a class of materials that combine hydrogen with other elements.
Other hydrides that superconduct at “high-temperatures” include a lanthanum hydride material, as well
as an yttrium hydride. While some researchers are eagerly pursuing
hydrides that work at ambient pressures, others say the field is moving too fast.
Skeptics raise several concerns, among them that hydrides haven’t demonstrated a key
component of superconductivity: the ability to push away magnetic fields,
also known as the Meissner effect.
The high-pressure of hydrides make it difficult to measure the Meissner effect.
Instead, researchers have tested magnetic susceptibility,
how magnetic an object becomes when exposed to a magnetic field.
Other superconductors become less magnetized as temperature decreases.
But carbonaceous sulfur hydride doesn’t follow this trend: they initially became less magnetized below
the critical temperature where the material begins to superconduct.
After further cooling, the reverse happened. Critics say this suggests that either hydrides
are not superconductors, or that they operate differently than other groups of superconductors.
If the hydrides are superconductors, scientists think two strategies could make them work
at lower pressures: chemical combinations with spare electrons to move through the material
and stabilizing the structure so it doesn’t need external pressure to stay locked in place.
So far, they have discovered two promising classes of hydrides with different 3D structures.
One is a cage of hydrogen atoms surrounding a heavy metal atom, which supplies lots of electrons.
The other creates a stronger, interlocking grid by combining hydrogen and other light
elements, such as sulfur.
While researchers are still working to replicate the 2020 finding,
the group behind the CSH discovery has already teased results of a
hydride that could function at way lower pressures. Even lower pressures, and diamonds won’t
have to be sacrificed to create hydride superconductors in the future.