Which is a room temperature superconductor

First superconductor at room temperature

Superconductors promise numerous technical applications, as they conduct electrical current without any resistance and without losses. So far, however, they cannot be used to transmit electricity on a large scale. This is because the available materials have to be cooled to around minus 200 degrees Celsius in order to switch to the superconducting state. But now physicists are presenting for the first time in the journal “Nature” a superconductor that conducts electrical current under high pressure at room temperature without resistance.

“To develop a superconductor for high temperatures, you need strong bonds and light elements,” says Ranga Dias of Rochester University. Therefore, together with his colleagues, he concentrated on the lightest element in the periodic table, which also has very strong bonds: hydrogen. First, the researchers used a laser-assisted reaction to produce a carbon-rich sulfur hydride with high proportions of hydrogen from hydrogen, sulfur and carbon. In order to turn this material into a superconductor, extremely high pressure was required, which the researchers generated with the help of a so-called diamond anvil cell.

At a transition temperature of 15 degrees Celsius - i.e. room temperature - and at a pressure of 267 gigapascals - which is 2.5 million times the atmospheric pressure - the electrical resistance in the sample sank to zero. The researchers thus achieved a new record. Dias and his colleagues also examined another characteristic phenomenon. Because a superconductor completely displaces an external magnetic field from within. The experiments showed that at a pressure of 189 gigapascals and the correspondingly lower transition temperature of minus 75 degrees Celsius, a magnetic field could no longer propagate in the sulfur hydride. This feature could not be checked at higher temperatures because the higher pressure required for these tests could not be built up experimentally.

Despite the new record, the carbon-rich sulfur hydride is not yet suitable for power lines. Technically, such high pressures can only be exerted on small samples in diamond press cells. But Dias and his colleagues hope to reduce the pressure required for the superconducting state at room temperature in the future by changing the composition of the hydrogen compounds. Should this succeed, not only loss-free power lines are conceivable. Such superconductors could also be used for very fast magnetic levitation trains, more powerful magnetic resonance tomographs and even special quantum computers.