Graphene switches: Team makes it to first base

Nov 27, 2012
Scanning tunneling microscopy shows the topography of graphene on gold with periodic beatings ten times larger than the periodicity of the carbon atoms. These beatings are moiré-patterns, emerging because of the different atomic structures of graphene and the underlying monolayer of gold atoms. The structure of moiré 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), Jülich (Germany) and Harvard (USA). According to their report on 27. November 2012 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 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 . Just like the earth, electrons have two angular momenta: an orbital angular momentum, which allows them to circle the ; 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 ), 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 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.

Explore further: Thinnest feasible nano-membrane produced

More information: DOI: 10.1038/ncomms2227

Related Stories

Physicists explore properties of electrons in graphene

Aug 10, 2012

Scientists from Georgia State University and the Georgia Institute of Technology have found a new way to examine certain properties of electrons in graphene – a very thin material that may hold the key to new technologies ...

Creating a pure spin current in graphene

Feb 07, 2011

(PhysOrg.com) -- Graphene is a material that has the potential for a number of future applications. Scientists are interested in using graphene for quantum computing and also as a replacement for electronics. However, in ...

New spin on graphene

Apr 14, 2011

(PhysOrg.com) -- University of Manchester scientists have found a way to make wonder material graphene magnetic, opening up a new range of opportunities for the world’s thinnest material in the area of ...

New technique controls graphite to graphene transition

Jul 02, 2012

(Phys.org) -- University of Arkansas physicists have found a way to systematically study and control the transition of graphite, the “lead” found in pencils, to graphene, one of the strongest, lightest ...

Graphene mini-lab

Oct 31, 2012

A team of physicists from Europe and South Africa showed that electrons moving randomly in graphene can mimic the dynamics of particles such as cosmic rays, despite travelling at a fraction of their speed, in a paper about ...

Recommended for you

Thinnest feasible nano-membrane produced

Apr 17, 2014

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...