New Atom-Related Research Could Pave Way for More Environmentally Friendly Data Storage

A group of researchers at the University of Tokyo, including Ibuki Taniuchi, Ryota Akiyama, Rei Hobara, and Shuji Hasegawa, have made a surprising discovery. They showed that in a single-atom layer of thallium-lead alloys, the spin-polarized current can be made to flow in only one direction when exposed to light at room temperature.

This discovery is unexpected because such thin layers were believed to interact very little with light, almost as if they were transparent. The original paper can be found here.

The ability to control the flow of current in one direction is key to modern electronics, especially in devices like diodes. Diodes allow current to flow only one way, and making them thinner and more efficient is a challenge for researchers. This new finding could lead to advancements in eco-friendly data storage and the development of ultra-thin two-dimensional spintronic devices.

Akiyama explained, ‘Spintronics usually focuses on thicker materials, but we were curious about thin systems because they have exciting properties. We wanted to see how light could be converted to spin-polarized current in such thin layers.’

The process they studied is called the circular photogalvanic effect (CPGE), where light creates a current with electrons spinning in the same direction. This causes the current to flow in just one direction, similar to how traditional diodes work but with light instead of voltage.

The researchers tested this in ultra-thin thallium-lead alloys under ultra-high vacuum conditions to avoid contamination and get clear results.

When they shone circularly polarized light on the material, they noticed not just a change in current direction but also that the current was spin-polarized. Akiyama found this particularly surprising because it aligned the electron spins with the current flow, thanks to the unique properties of these thin alloys.

These alloys were initially developed by the team for another purpose, but their unusual electronic behavior hinted at this new possibility. Excited by these findings, Akiyama and his team plan to explore further by using lower-energy lasers to refine the CPGE process and improve how efficiently light can be turned into spin-polarized current.

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