Laser Light Transforms Material into a Superconductor

For decades researchers have been searching for a way to achieve superconductivity other than bringing special materials down to a temperature near absolute zero.

Now Oxford University researchers report non-superconducting material can be made a superconductor by using laser light. Professor Andrea Cavalleri of the Department of Physics at Oxford University—and the Max Planck Department for Structural Dynamics, Hamburg, Germany—worked with a team from Germany and Japan. They confirmed signatures of superconductivity after beaming intense laser light at a non-superconducting material.

Superconductivity, discovered 100 years ago in 1911, has been difficult to reach and maintain. Its uses have been limited because of the regiment that must be met to achieve the state allowing electricity to flow with virtually no resistance.

The team describes in a paper published in the journal Science how they used a powerful infrared laser pulse to excite the atoms in material closely related to high-temperature copper oxide superconductors. This compound, however, is normally a non-conductive material.

After hitting the material—lowered to a temperature 20 degrees above absolute zero—with a strong laser pulse, however, it became a superconductor almost instantaneously. The effect was brief, lasting ony fractions of a second. Nevertheless, it was a significant breakthough and demonstrates that atoms in nonconducting materials can be perturbed into a state making them conducive towards superconductivity.

“We have used light to turn a normal insulator into a superconductor,” Cavalleri told Science for their media report. “That’s already exciting in terms of what it tells us about this class of materials. But the question now is can we take a material to a much higher temperature and make it a superconductor?”

Room-temperature superconductors – the “Holy Grail” of physics

Because several false claims were made about the discovery of a material with the properties of room-temperature superconductivity during the past decade, most condensed matter physicists are wary of any such claim now.

To meet the conditions of a room-temperature conductor, the compound must be able to achieve super-conductive properties at temperatures above 32° F. Achieving this would make superconductivity virtually ubiquitous in all power applications—better yet, it would make it cheap.

The best super-conductors today are made of copper oxides and must be cooled to temperatures around –274°F. Absolute zero—a theoretical temperature where entropy reaches its minimum value—is thought to be attained at –459.67°F. That temperature has never been obtained because it cannot be done using only thermodynamic means.

“We have shown that the non-superconducting state and the superconducting one are not that different in these materials, in that it takes only a millionth of a millionth of a second to make the electrons ‘synch up’ and superconduct,” said Cavalleri. “This must mean that they were essentially already synched in the non-superconductor, but something was preventing them from sliding around with zero resistance. The precisely tuned laser light removes the frustration, unlocking the superconductivity.”

Although the breakthrough opens the door to discovering exactly how superconductivity works in various classes of materials, a greater promise is that the approach may eventually lead to the elusive room-temperature super-conductor.

As Cavalleri neatly sums it up in the Science interview: “There is a school of thought that it should be possible to achieve superconductivity at much higher temperatures, but that some competing type of order in the material gets in the way. We should be able to explore this idea and see if we can disrupt the competing order to reveal superconductivity at higher temperatures. It’s certainly worth trying!”