Spin dynamics of graphene explained through supercomputing

August 2, 2017
Credit: ICN2

In a previous study, researchers found evidence to suggest that spin-orbit coupling (SOC) was greater in graphene/transition metal dichalcogenide heterostructures than in regular graphene. In principle, this phenomenon is a necessary prerequisite for the spin Hall effect (SHE), yet subsequent tests to measure the system's SHE gave inconclusive results. In a paper published this July in NanoLetters, researchers of the ICN2 Theoretical and Computational Nanoscience Group, led by ICREA Prof. Stephan Roche, were able to confirm the observations of an enhanced SOC, as well as propose a reasonable explanation as to why the SHE could not be measured experimentally.

Spintronics is a branch of electronics that uses the spin of subatomic particles like electrons to store and transport information, and not just the charge as with conventional electronics. The result is devices that are faster, operate at a fraction of the energy cost and have vastly larger memory capacities. The spin Hall effect is what allows us to create and manipulate the spin, and generate a . But in the previous experiment, although the SHE was taking place, the resulting spin current could barely be detected.

What ICN2 researchers did, thanks to access to the Barcelona Supercomputing Center's MareNostrum via an EU PRACE project, was to scale-up the experiment, conducting detailed and realistic simulations at the micrometer scale. As first author of the paper Dr. Jose H. García Aguilar explains, by doing so they were able to show that the conditions that enabled observation of enhanced SOC were not the same as those required to observe the SHE. Specifically, to observe the former, you need the material to be structurally defective, which creates disorder and high inter-valley scattering as the charge passes through the material. However, this high level of disorder, which emerged as significant only once the experiment had been simulated on a larger scale, was suppressing the spin current generated through the SHE, leading to the inconclusive results reported.

This study offers new insights into the spin dynamics unique to graphene, and allows us to propose new paths to achieving SHE-induced spin current experimentally in graphene-based heterostructures.

Explore further: Pseudospin-driven spin relaxation mechanism in graphene

More information: Jose H. Garcia et al. Spin Hall Effect and Weak Antilocalization in Graphene/Transition Metal Dichalcogenide Heterostructures, Nano Letters (2017). DOI: 10.1021/acs.nanolett.7b02364

Related Stories

Pseudospin-driven spin relaxation mechanism in graphene

November 12, 2014

The prospect of transporting spin information over long distances in graphene, possible because of its small intrinsic spin–orbit coupling and vanishing hyperfine interaction, has stimulated intense research exploring spintronics ...

Spin currents switch at terahertz frequencies

July 5, 2017

The technology of spintronics is based on the intrinsic spin of electrons. In the medium term, it is set to replace electronics as the basis for technical devices. DESY scientist Lars Bocklage has discovered a new way of ...

The spin in graphene can be switched off

July 5, 2017

By combining graphene with another two-dimensional material, researchers at Chalmers University of Technology have created a prototype of a transistor-like device for future computers, based on what is known as spintronics. ...

Spin-resolved oscilloscope for charge and spin signals

March 13, 2017

Researchers at the Tokyo Institute of Technology and Nippon Telegraph and Telephone Corporation have developed a "spin-resolved oscilloscope." This device is a basic measuring instrument for plasmonics and spintronics, which ...

Recommended for you

Clothing fabric keeps you cool in the heat

November 16, 2017

(Phys.org)—Researchers have designed a thermal regulation textile that has a 55% greater cooling effect than cotton, which translates to cooler skin temperatures when wearing clothes made of the new fabric. The material ...

Semiconductors with an aligned interface

November 13, 2017

The electronic characteristics of an interface between two wide bandgap semiconductors are determined by researchers at KAUST: an insight that will help improve the efficiency of light-emitting and high-power electronic devices.

Zipping DNA

November 13, 2017

ETH researchers have developed a method that allows large amounts of genetic information to be compressed and then decompressed again in cells. This could aid in the development of new therapies.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.