Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Semiconductor physics: Taking control of spin

01.02.2013
Generating and sustaining electrical currents with unique properties for information processing comes closer to reality after a successful theoretical demonstration

Sustaining a spin-polarized current, in which the spin (depicted as an arrow) of each electron (yellow) is aligned, is integral to advancing spintronic applications



Copyright : 2013 A*STAR Data Storage Institute

Spintronics is a form of signal processing similar to that used in traditional electronics, but it takes advantage of a property of electrons known as spin. Spin is often visualized as an arrow about which the electron rotates, much like a top spinning around its axis. Generating a stream of electrons in which these 'arrows' are all parallel - a so-called spin-polarized current (see image) - is the foundation upon which spintronics is based. Imperfections in a material, however, can easily destroy polarization.

Simply applying an oscillating voltage across the device could help to maintain a spin-polarized current even in the presence of impurities, according to theoretical research by Seng Ghee Tan at the A*STAR Data Storage Institute, Singapore, and co©workers

Tan and his colleagues considered a two-dimensional electron gas: a system in which the electrons can move only in one plane. When a spin-polarized current flows through such a material, the spins interact with the electron's motion through an effect known as Rashba spin¨Corbit coupling. This makes the spins start to 'wobble' or precess: at first they point upwards but then point downwards, and this reduces the total spin polarization to zero. "We want to prolong the life span of a spin current in the channel by controlling the strength of the Rashba coupling," says Tan. To this end, he and his team investigated a device, known as a spin-current rectifier, that lets a spin current flow with one particular polarization - upwards only, for example.

The researchers developed a simple mathematical equation that predicts the behavior of the spin current as an alternating voltage is applied across the device. Their model shows that when the frequency of the voltage is zero, the spin polarization goes back and forth as expected. "However, by increasing the frequency, we see an increasingly asymmetrical pattern of oscillation in favor of positive polarization," explains Tan. "We call this a gradual process of rectification."

Their approach can even suppress precessional motion entirely. When the external modulation frequency is much faster than the natural precessional frequency of the spins, known as the Larmor frequency, the spins have no time to change direction so remain pointing upwards. Consequently, the system maintains a spin-polarized current.

Once spin currents can be sustained, spintronics will have all the potential of electronics with the additional advantage of an extra degree of control. The spin-current rectifier investigated by Tan and his co-workers could therefore become a vital component in this future technology.

The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute
Associated links
http://www.research.a-star.edu.sg/research/6619
Journal information
Ho, C. S., Jalil, M. B. A. & Tan, S. G. Sustainable spin current in the time-dependent Rashba system. Journal of Applied Physics 111, 07C327 (2012).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg/research/6619
http://www.researchsea.com

More articles from Power and Electrical Engineering:

nachricht Early Warning System for Dikes Passes Field Test
17.11.2014 | Siemens AG

nachricht Test runs started for the BorWin2 grid link
13.11.2014 | Siemens AG

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Anzeige

Anzeige

Event News

Educating the Ecucators

13.11.2014 | Event News

36th Annual IATUL Conference 2015: Call for papers and posters

12.11.2014 | Event News

Outstanding Young Researchers Meet At Heidelberg Center for Latin America

11.11.2014 | Event News

 
Latest News

Siemens and LG Chem plan closer collaboration on battery storage systems

20.11.2014 | Press release

Lighting up tumors

20.11.2014 | Life Sciences

From Architect to Social Worker: Complex Jobs May Protect Memory and Thinking Later in Life

20.11.2014 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>