Physicists demonstrate using non-polarized light to produce spin voltage in metal for first time

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Physicists demonstrate using non-polarized light to produce spin voltage in metal for first time

Post by Cr6 on Tue Apr 26, 2016 12:37 am

Physicists demonstrate using non-polarized light to produce spin voltage in metal for first time

April 25, 2016

(More at link....)

With apologies to Isaac Asimov, the most exciting phase to hear in science isn't "Eureka," but "That's funny..." A "that's funny" moment in a Colorado State University physics lab has led to a fundamental discovery that could play a key role in next-generation microelectronics.

Publishing in Nature Physics April 25, the scientists, led by Professor of Physics Mingzhong Wu in CSU's College of Natural Sciences, are the first to demonstrate using non-polarized light to produce in a metal what's called a spin voltage - a unit of power produced from the quantum spinning of an individual electron. Controlling electron spins for use in memory and logic applications is a relatively new field called spin electronics, or spintronics, and the subject of the 2007 Nobel Prize in Physics.

Wu and his group's passion is to find new, better ways to control electron spins, the physics of which isn't completely understood. Spintronics exploits the notion that electron spins can be manipulated and used to process and store information, with a fraction of the power needed in ubiquitous, conventional electronics.
Consider that the iPhone and every electronic device out there is built upon centuries of science around charge current - the physics of positive or negative charges flowing through a device. The perennial problem is the enormous power consumption of charge-current devices, and the electrical resistance that causes power loss in the form of heat - which is why your laptop keeps overheating.

It's these power and heat barriers that are holding smaller, more powerful electronics back. And it's why science is turning to spintronics, because it offers a completely new way of making a device work. To utilize power from an electron spin, there's no charge current necessary. All that's needed is a magnetic field or a magnetic material, which can orient the spins "up" or "down." The up and down spins are the analogue to positive and negative charges.

What the CSU scientists have found is a brand-new method for creating spin currents. Existing methods include using a charge current, microwaves or a heat source. But for the first time, the CSU team demonstrates using light - or in the quantum world, photons - to generate their spin currents.

Other scientists have done similar things, but they used a special kind of polarized light. Here, the CSU scientists used unpolarized, plain light - "a halogen bulb purchased at Ace Hardware," said graduate student David Ellsworth who is the first author on the paper. They demonstrated a "pure" spin current - involving no charge movement whatsoever. It was an unprecedented feat.

"The framework for generating and detecting spin currents is non-trivial," Ellsworth 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."
Explore further: Ultrafast heat conduction can manipulate nanoscale magnets
More information: Photo-Spin-Voltaic Effect, Nature Physics, DOI: 10.1038/nphys3738


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