Mar 29 2018
Graphene nanoflakes, tiny and very favorable for probable applications in the field of nanoelectronics, are being investigated by a SISSA’s team. The nanoflakes feature in a research published recently in the Nano Letters journal. These hexagonal-shaped nanostructures can be used to exploit quantum effects to control the current flow.
As a result of their intrinsic magnetic properties, they could also signify an important step forward in the field of spintronics, which is based on the electron spin.
On the left: Spin filter made out of a magnetic nanoflake: a current of electrons with spin "up" and "down" in equal proportions flows through the device. Due to destructive interference in a spin channel (for example: down) the outgoing current is prevalently made of spin-up electrons. On the right: Schematic illustration of the device and plot of the spin-filtering efficiency. (Image credit: Angelo Valli)
The research, conducted by theoretical analysis and simulations on a computer, was led by Massimo Capone, newly appointed Outstanding Referee by Physical Review Letters, the prestigious journal of the American Physical Society.
“We have been able to observe two key phenomena by analyzing the properties of graphene nanoflakes. Both are of great interest for possible future applications” explain Angelo Valli and Massimo Capone, authors of the research paper along with Adriano Amaricci and Valentina Brosco.
The first phenomenon deals with the supposed interference between electrons and is a quantum occurrence: “In nanoflakes, the electrons interfere with each other in a “destructive” manner if we measure the current in a certain configuration. This means that there is no transmission of current. This is a typically quantum phenomenon, which only occurs at very reduced sizes. By studying the graphene flakes we have understood that it is possible to bring this phenomenon to larger systems, therefore into the nano world and on a scale in which it is observable and can be exploited for possible uses in nanoelectronics”.
The two researchers elucidate that in what are called “Quantum interference transistors” damaging interference would be the “OFF” status. For the “ON” status, they say it is enough to eliminate the conditions for interference, thus enabling the current to flow.
Magnetism and Spintronics
Furthermore, in the study, the team showed that the nanoflakes present new magnetic properties which are absent, for instance, in a whole sheet of graphene: “The magnetism emerges spontaneously at their edges, without any external intervention. This enables the creation of a spin current”. The union between the phenomena of quantum interference and of magnetism would enable attaining almost full spin polarization, with an enormous potential in the field of spintronics, explain the researchers. These properties could be used, for instance, in the memorizing and processing information technologies, deducing the spin as binary code. The electron spin, being quantized and having only two possible configurations (which can be called “up” and “down”), is highly suited for this kind of execution.
Next Step: The Experimental Test
To enhance the efficiency of the potential device and the percentage of current polarization the researchers have also formed a protocol that envisions the interaction of the graphene flakes with a surface made of boron and nitrogen.
“The results obtained are really interesting. This evidence now awaits the experimental test, to confirm what we have theoretically predicted” concludes Massimo Capone, head of the research and recently awarded the title of Outstanding Referee by the American Physical Society journal.