Research explores magnetic fields of superconducting materials

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As a young Israeli scholar, Ron Folman was fascinated by the properties of a small disk of superconducting material he created during an experiment. Declining to discard it, he took it to a jeweler in Jerusalem, wanting to make a necklace for his girlfriend.

“This is the metal of the future,” he told the jeweler.

Thirty years later, Folman, a visiting professor from Ben-Gurion University of the Negev in Israel, along with a team of researchers from UC Berkeley and Ben-Gurion, published a research paper in Physical Review B last month in which the magnetic fields in these superconducting materials, which show zero electrical resistance when chilled, have been further unveiled.

The research follows the work of Lawrence Berkeley National Laboratory, UC Berkeley and Harvard University, one of many around the world who pioneered the use of this sensor. Now, UC Berkeley researchers led by campus physics professor Dmitry Budker — an expert in magnetic sensors — along with the Israeli team, led by Folman — an expert in integrated chips — have taken the next step to study the magnetic fields of high-temperature superconducting materials using the highly sensitive altered diamonds.

“The diamonds can operate at any temperature, from absolute zero to many degrees celsius,” Budker said. “This is one of its advantages against some of its competitors.”

For their experiment, researchers bombarded the diamonds with nitrogen atoms that knock out some of the carbon atoms that make up the pure diamond structure, leaving holes or nitrogen atoms in their place. The combination of a nitrogen atom and a hole create what is called a negatively charged nitrogen vacancy center, or “NV- center,” with the minus standing for the extra electron that makes the diamond hypersensitive to magnetism.

The project was initiated by the two group leaders and a colleague from UCLA and mainly carried out in Israel by former doctoral student Amir Waxman. The artificial, colored diamonds were incorporated into an integrated chip that is able to read the magnetic vortices created in the superconducting material. Data were then recorded through a technique called laser spectroscopy.

“We shine green light at the diamonds, and we get back red light from them,” Folman said. “By looking at the features of the red light — its intensity for example — we could know what kind of magnetic field the NV- sensor is feeling.”

Even though these superconductors are considered high-temperature in the physics field, the ones used in this work still need to be chilled at approximately -330 degrees Fahrenheit to work. Budker and Folman are working toward understanding the behavior of these materials so that in the future, room-temperature superconductors can be developed.

“With this research, we believe that once we solve the intellectual puzzle, it will be a great new technology for people to use,” Folman said. “Room-temperature superconductors could be the base for very strong magnets, making trains hover, for example.”

Contact Robin Simmonds at [email protected] and follow her on Twitter @@rsimmonds_dc.

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