The birth of spinplasmonics

The birth of spinplasmonics

Summary: You might have heard of spintronics, a technology that uses the magnetic quantum properties of the spin of electrons, or plasmonics, another one which 'involves the transfer of light electromagnetic energy into a tiny volume, thus creating intense electric fields.' Now, researchers at the University of Alberta have merged these two nascent research fields to create a new nanotechnology field called spinplasmonics. According to the researchers, this new technology, which was already used to control the quantum state of an electron's spin to switch a beam of terahertz light, could one day be the basis for 'computers with extraordinary capacities.'

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You might have heard of spintronics, a technology that uses the magnetic quantum properties of the spin of electrons, or plasmonics, another one which 'involves the transfer of light electromagnetic energy into a tiny volume, thus creating intense electric fields.' Now, researchers at the University of Alberta (U of A) have merged these two nascent research fields to create a new nanotechnology field called spinplasmonics. [Note: And when I say 'new,' it really is: Google returned only 25 pages containing the word spinplasmonics today.] According to the researchers, this new technology, which was already used to control the quantum state of an electron's spin to switch a beam of terahertz light, could one day be the basis for 'computers with extraordinary capacities.'

Spinnning plasmonics

On the diagram above, you can see how "terahertz light is partially transmitted through the material via plasmons on the surface of cobalt particles, which are partially coated with gold (top). If the cobalt is magnetized by an applied magnetic field, electrons can be spin polarized by the light (bottom). This reduces the amount of light that is transmitted through the material. (Credit for image: Abdul Elezzabi, University of Alberta; credit for caption: PhysicsWeb).

After this rather technical introduction, let's return to the U of A news release for an explanation in -- almost -- plain English.

The new technology, which the researchers call spinplasmonics, may be used to create incredibly efficient electron spin-based photonic devices, which in turn may be used to build, for example, computers with extraordinary capacities. "We've only just begun to scratch the surface of this field, but we believe we have the physics sorted out and one day this technology will be used to develop very fast, very small electronics that have a very low power consumption," said [Abdulhakem] Elezzabi, the Canada Research Chair in Ultrafast Photonics and Nano-Optics and an electrical and computer engineering professor at the U of A.

In "Merging Spintronics and Plasmonics: Evidence of Spinplasmonics," the 2Physics blog added on April 17, 2007 that Elezzabi and his collagues teamed up with the U.S. Naval Research Laboratory to "demonstrate a novel approach for the active control of terahertz plasmonic propagation."

Using an ensemble of sub-wavelength size ferromagnetic/nonmagnetic spintronic structures, their experiments provide the first evidence of low frequency plasmonic conduction controlled via the electron-spin. Such phenomenon can be conceptualized as the photonic analog to the electrically-driven spin accumulation that serves as a basis for spintronic devices.

The 2Physics blog entry also contains a very informative conceptual illustration of a nonresonant particle plasmon and describes the future uses of spinplasmonics.

The demonstration of a spin-dependent photonic phenomenon opens up a novel avenue in both the fields of spintronics and photonics. The ability to magnetically manipulate near-field mediated light transport on metallic particles via electron spin promises another degree of freedom in the design of photonic devices. The researchers envision the development of solid-state, magnetically sensitive terahertz photonic switches, modulators, and band-pass filters based on electron spin.

In a PhysicsWeb article, "Spins turn light off," Hamish Johnston gives additional details (April 9, 2007; free registration required). The above illustration has been picked from this article.

Many researchers are trying to develop "spintronic" devices that use the spin of the electron as well as its electrical charge to store and process information. Others, meanwhile, are trying to exploit the interaction between light and the collective oscillations of electrons on the surfaces of metals (called plasmons) to create “plasmonic” devices for processing and transmitting data. Now, Abdul Elezzabi and Kenneth Chau at the University of Alberta, along with Mark Johnson at the Naval Research Laboratory in Washington, DC, have created a material that combines spintronics and plasmonics to switch a beam of terahertz light.

Finally, this research work has recently been published by Physical Review Letters under the title "Electron-Spin-Dependent Terahertz Light Transport in Spintronic-Plasmonic Media" (Volume 98, Number 13, Article 133901, March 29, 2007). Here is a link to the abstract.

Sources: University of Alberta, May 29, 2007; and various websites

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