Featured Research

from universities, journals, and other organizations

Graphene switches: Research group makes it to first base

Date:
November 27, 2012
Source:
Helmholtz Association of German Research Centres
Summary:
Ever since graphene was first isolated a few years ago, this quasi-two-dimensional network made up of a single layer of carbon atoms has been considered the magic material. Not only is graphene mechanically highly resilient, it also provides an interesting basis for new spintronic components that exploit the magnetic moment of conduction electrons. Now researchers have successfully managed to increase the graphene conduction electrons' spin-orbit coupling by a factor of 10,000 -- enough to allow them to construct a switch that can be controlled via small electric fields.

The picture shows the topography of graphene on gold with periodic beatings ten times larger than the periodicity of the carbon atoms. These beatings are moirι-patterns, emerging because of the different atomic structures of graphene and the underlying monolayer of gold atoms. The structure of moirι influences chemical interactions between gold and graphene layer and also electronic properties and spin behavior in graphene.
Credit: HZB/Andrei Varykhalov

Ever since graphene was first isolated a few years ago, this quasi-two-dimensional network made up of a single layer of carbon atoms has been considered the magic material. Not only is graphene mechanically highly resilient, it also provides an interesting basis for new spintronic components that exploit the magnetic moment of conduction electrons.

Now, Helmholtz Centre Berlin's Dr. Andrei Varykhalov, Prof. Dr. Oliver Rader and his team of physicists has taken the first step towards building graphene-based components, in collaboration with physicists from St. Petersburg (Russia), Jόlich (Germany) and Harvard (USA). According to their Nov. 27 report in Nature Communications, they successfully managed to increase the graphene conduction electrons' spin-orbit coupling by a factor of 10,000 -- enough to allow them to construct a switch that can be controlled via small electric fields.

The graphene layer sits on top of a nickel substrate whose atoms are separated by the same distance as graphene's hexagonal meshes. Next, the physicists deposited gold atoms on their sample that ended up lodging between the graphene and the nickel.

Using different photoelectron spectrometers at HZB's own BESSY II synchrotron radiation facility allowed the researchers to measure changes in graphene's electronic properties. Just like Earth, electrons have two angular momenta: an orbital angular momentum, which allows them to circle the atomic nucleus; and a spin corresponding to a rotation about their own axes. A strong spin-orbit coupling thus means a big energetic difference depending on whether both rotations are directed in the same or in opposite directions. In the case of lighter nuclei (as is true for carbon atoms), the spin-orbit interaction is rather weak, whereas in the case of heavier atoms like gold it is quite strong. "We could show that, given their proximity to the graphene layer, the gold atoms were also able to increase this interplay in the graphene layer by a factor of 10,000," explains Dmitry Marchenko who took the measurements as part of his Ph.D. research.

According to Varykhalov, this very strong spin-orbit coupling would allow the researchers to build a switch of sorts as the spins could now be rotated using an electric field. Two spin filters -- one in front of and one behind the component -- would each tolerate unidirectional spins only. If the spin filters were perpendicular to each other, no spin would be able to get through anymore and the switch would be effectively shut off. An electric field, however, would rotate the spins in such a way that it would be able to -- partially or completely -- turn up the switch.

"We were able to document that only electrons in the 5d orbitals of gold atoms increase graphene's spin orbit interaction. This conforms to our theoretical models," explains Varykhalov. Nonetheless, the HZB physicists have their next challenge cut out for themselves already: a graphene-based component that sits on a non-conducting surface instead of nickel, a metal. Not surprisingly, they have already begun working on it.


Story Source:

The above story is based on materials provided by Helmholtz Association of German Research Centres. Note: Materials may be edited for content and length.


Journal Reference:

  1. D. Marchenko, A. Varykhalov, M.R. Scholz, G. Bihlmayer, E.I. Rashba, A. Rybkin, A.M. Shikin, O. Rader. Giant Rashba splitting in graphene due to hybridization with gold. Nature Communications, 2012; 3: 1232 DOI: 10.1038/ncomms2227

Cite This Page:

Helmholtz Association of German Research Centres. "Graphene switches: Research group makes it to first base." ScienceDaily. ScienceDaily, 27 November 2012. <www.sciencedaily.com/releases/2012/11/121127111340.htm>.
Helmholtz Association of German Research Centres. (2012, November 27). Graphene switches: Research group makes it to first base. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2012/11/121127111340.htm
Helmholtz Association of German Research Centres. "Graphene switches: Research group makes it to first base." ScienceDaily. www.sciencedaily.com/releases/2012/11/121127111340.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) — British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) — Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) — A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) — Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins