Vortex pinning could lead to superconducting breakthroughs

The team discovered a way to efficiently stabilize tiny magnetic vortices that interfere with superconductivity -- a problem that has plagued scientists trying to engineer real-world applications for decades. The discovery could remove one of the most significant roadblocks to advances in superconductor technology.

Superconductors are extremely useful materials, given that modern society involves moving a lot of electricity around. Each time we do it, whether it be along the cord from the outlet to your lamp or in the millions of miles of power lines strung across the country, we lose a little bit of electricity. That effect is due to resistance in the wires we currently use to transport electricity. Even a pretty good conductor, like copper wire, loses some electricity due to resistance.

But in an ideal superconductor, no electricity is ever lost. If you set up a loop of perfect superconducting wire and added some current, it would circle that loop forever. Superconductors are the secret behind MRI machines, Maglev trains and improved cell phone reception.

The problem is that superconductors have to be cooled to do their thing. Even the "high-temperature" superconductors already discovered have to be chilled to -280° Fahrenheit. That creates a lot of engineering and logistical problems.

In the long run, scientists are hoping to develop superconducting materials that would operate closer to room temperature. That would be a major achievement -- though it is generally still thought to be a long way off.

In the meantime, there remain key problems of superconductivity that need to be solved even in the low-temperature environment.

One such major problem is posed by magnetic fields. When magnetic fields reach a certain strength, they cause a superconductor to lose its superconductivity. But there is a type of superconductor -- known as "Type II" -- which is better at surviving in relatively high magnetic fields. In these superconductors, magnetic fields create tiny whirlpools or "vortices." Superconducting current continues to travel around these vortices to a point, but eventually, as the magnetic field strengthens, the vortices begin to move about and interfere with the material's superconductivity, introducing resistance.

"These vortices dissipate the energy when moving under applied currents and bury all hopes for a technological revolution -- unless we find ways to efficiently pin them," said Argonne Distinguished Fellow Valerii Vinokur, who co-authored the study.

Scientists have spent a lot of time and effort over the past few decades trying to immobilize these vortices, but until now, the results have been mixed. They found ways to pin down the vortices, but these only worked in a restricted range of low temperatures and magnetic fields.