Yale Daily News

A group of Yale researchers has made the first accurate measurements of a constant electric current that flows through metals without applied voltage.

In a study published in the Oct. 9 issue of Science, Yale researchers demonstrated that electric currents can flow continuously through resistant objects such as metals without dissipating energy. The finding, which was validated with precise measurement of a current through tiny metal rings, resolves nearly two decades of contradictory findings in the field.

“The idea that electrons flow around a nucleus of an atom is an old idea,” physics professor Jack Harris said. “What we were trying to ask is: can that same motion of electrons occur in a much, much larger scale? Can it occur in a solid object resistant object like metal?”

While quantum mechanics predicts that electrons at the ground state — the lowest energy level of the electron — move around randomly, the idea that electrical currents can flow consistently through resistant objects like metal was a “pretty revolutionary insight” in the 1980s, Harris said.

But for the longest time, theory and evidence did not agree with each other. Because their instruments were not sensitive enough, researchers found persistent current flows 100 times larger than expected, said team member William Shanks GRD ’11, a physics graduate student.

Harris and his team started their research on persistent current over four years ago. They used cantilevers, which measure the force of movements in a magnetic field, to detect electric current as it flowed in different directions through aluminum rings. Even when they varied their experiment over a wide range of temperatures, ring sizes and magnetic fields, they still found a flowing current.

Their findings, Harris said, will help scientists to better understand how other quantum theories work, such as how metals could be used as superconductors, which are materials that have zero electrical resistance at very low temperatures..

“It’s always interesting to check the weird predictions that quantum physics seems to make — it’s good to resolve controversy,” Harris said. “But this research is important because it helps to better our understanding of how electrons work and how it could affect our society.”

Besides Shanks, Harris’ team includes researchers Ania Bleszynski-Jayich and Eran Ginossar, Visiting master’s student Bruno Peaudecerf, physics professor Leonid Glazman, and Freie Universität Berlin physics professor and theorist Felix von Oppen.