A Brand-new Way to Produce Electron Spin Currents

Estimated reading time: 4 minutes

The breakthrough came about while the scientists were studying spin currents created by the heat from their Ace Hardware bulb. They noticed some background data they couldn’t explain: the “that’s funny” moment.

Ever curious, they checked all possibilities and determined that this seemingly light-induced spin current could be a new quantum phenomenon. They tested it by designing unique control measurements involving different magnetic insulators and metallic thin films, such as platinum. After replicating their results in the lab, they turned to theoreticians at the University of California Irvine and Fudan University to help them interpret the physics of what they’d discovered. These experts became co-authors on the Nature Physics paper.

Wu said the discovery is too new to think about real-world applications; scientists are continuing to make breakthroughs in the theoretical understanding of spin currents. “Just like with the photovoltaic effect when it was first discovered, no one thought at first of a solar cell,” Wu said. “Technologies take time before they are used in real devices. This is a fundamental, new discovery.”

Said Jake Roberts, chair of the CSU Department of Physics: “There have been tremendous technical advances in controlling light. What I see in this discovery is that now, they’ve linked light to spin control. Using a simple light source to produce a spin current offers new opportunities for power control and generation.”

Continuing the Inquiry

The researchers will continue exploring making spin currents by swapping out materials and trying different light sources. They demonstrated light control in the infrared range, and moving into the visible or UV range would likely offer more robust applications for devices, Ellsworth said.

“The framework for generating and detecting spin currents is non-trivial,” he explained. “Meanwhile, there are hundreds of years of generating charge currents and knowing how to measure them and manipulate them and characterize them. Spintronics is a new field, and devices are just now coming onto the market that utilize some small part of this.”

The research was supported primarily by the U.S. Army Research Office, and was also supported by the Department of Energy and other funding agencies. The CSU team includes former graduate student Lei Lu, graduate student Houchen Chang and former postdoc Peng Li, as well as former undergraduate researcher Bryan Johnson and Poudre High School student Yuqi Bian, who joined Wu’s lab last summer through REAP (Research and Engineering Apprenticeship Program). Wu has mentored high school students through the REAP program since its inception in 2007.

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