A carbon cage for computer data


Spintronics offers new application possibilities for computer data storage, transfer and processing, but the technology’s main drawback is the instability of spin information transport. In the journal Science Advances, UCLouvain and University of Paris researchers present a carbon nanostructure that addresses it.

Super Sonic? No, spintronics has nothing to do with Sega’s little hedgehog mascot. Energy and speed are essential to both, yes, but the analogy ends there.

Spintronics is a technology that uses the spin and charge of electrons to store, transport and process computer data. The technology allows stabler, faster data transport while reducing the energy required for it. The electron is an elementary particle that plays a major role in all the physical properties of matter such as electrical or thermal conductivity, mechanical properties, magnetism and luminescence. Much like the earth revolves around the sun, an electron spins while revolving around the atom’s nucleus. This simplistic image illustrates the purely quantum property, the electron’s spin, which is at the heart of spintronics.

Opening a technological lock

The amount of computer-processed data is growing exponentially and will continue to grow in the years to come, especially with the arrival of 5G. So many people possess countless photos and hours of videos or music on their smartphone or computer. Storing, reading, modifying, and recording all this information represents classic computer information processing. In order to optimise these processes, certain spintronic circuits, a quantum technology born in the 1980s, are used in practically all elements of information storage, whether in a magnetic hard disk or magnetic random access memory (MRAM). The problem is that while the storage of information in magnetic form has recently made tremendous progress, approaching 40 GB/cm², the transport of spin information on a chip remains delicate and very unstable. It’s practically impossible to transport without losing it (via decoherence) between the components on electronic cards. Opening this technological lock remains absolutely necessary to overcoming the current paradigm of computer architectures. This is what Aurélien Lherbier and Jean-Christophe Charlier of the UCLouvain Institute for Condensed Matter and Nanosciences (IMCN) have tackled with two University of Paris teams under the direction of Clément Barraud of the Materials and Quantum Phenomena Laboratory. The collaboration led to the creation of an artificial nanostructure allowing the transport of quantum information over long distances using spintronics, thus overcoming instability and considerably accelerating data processing speed. Study results will be published on 31 July in the journal Science Advances.

Protective carbon cage

Quantum information is inherently extremely fragile. While many theories have emerged in recent years concerning spin logic circuits, outperforming the competition in terms of energy consumption, an optimised information transport system was still lacking. This is the challenge that teams at the University of Paris Quantum Materials and Phenomena Laboratory and ITODYS Laboratory took up in collaboration with the IMCN’s Prof. Charlier and Research Associate Lherbier. They succeeded in generating a protective platform using multi-walled carbon nanotubes of which only the outer wall is chemically modified by molecules, like a cage.

The benefit of the nanotube’s chemical modification: it allows a very strong spin signal to be sent while isolating the spins toward the nanotube’s internal walls, which are naturally more protected against decoherence phenomena that dilute the original information. Dr Lherbier explains, ‘Calculations based on the experimental data appear to push the spin transport distance beyond a millimetre, as compared to a few tens and hundreds of micrometres previously measured in graphene, a very similar system.’ The technological advance could make it possible to create a new generation of quantum spin logic devices that extend the limits of current computer architectures by saving significant data-processing time and sharply reducing computer energy consumption.

Image : Illustration of a device made from a chemically modified multi-walled carbon nanotube on its outer layer and connected between two magnetic electrodes serving as a spin source and spin detector. The presence of molecules on the outer wall of the nanotube allows information to be concentrated in the inner walls. The speed of information movement is 5.105 m/s, 600 times slower than the speed of light.


Bio of Jean-Christophe Charlier

Published on July 31, 2020