Spintronics - Page 2

Two recent studies by a collaborative team of scientists from two NCCR MARVEL labs have identified a new type of defect as the most common source of disorder in on-surface synthesized graphene nanoribbons (GNRs).

Combining scanning probe microscopy with first-principles calculations allowed the researchers to identify the atomic structure of these so-called "bite" defects and to investigate their effect on quantum electronic transport in two different types of graphene nanoribbon. They also established guidelines for minimizing the detrimental impact of these defects on electronic transport and proposed defective zigzag-edged nanoribbons as suitable platforms for certain applications in spintronics.

Researchers from France, South Korea, and Japan have created a graphene-based beam splitter for electronic currents. The tunable device’s operation is directly comparable to that of an optical interferometer. The team believes that the technology could enable electron interferometry to be used in nanotechnology and quantum computing.
Quantum Hall valley splitter - schematic representation of the p − n junction. Image from article

An optical interferometer splits a beam of light in two, sending each beam along a different path before recombining the beams at a detector. The measured interference of the beams at the detector can be used to detect tiny differences in the lengths of the two paths. Recently, physicists have become interested in doing a similar thing with currents of electrons in solid-state devices, taking advantage of the fact that electrons behave similarly to waves in the quantum world.

An international research team, led by the University at Buffalo, has reported an advancement that could help give graphene magnetic properties. The researchers describe in their work how they paired a magnet with graphene, and induced what they describe as artificial magnetic texture in the nonmagnetic material.

The image shows eight electrodes around a 20-nanometer-thick magnet (white rectangle) and graphene (white dotted line). Credit: University at Buffalo.

Independent of each other, graphene and spintronics each possess incredible potential to fundamentally change many aspects of business and society. But if you can blend the two together, the synergistic effects are likely to be something this world hasn’t yet seen, says lead author Nargess Arabchigavkani, who performed the research as a PhD candidate at UB and is now a postdoctoral research associate at SUNY Polytechnic Institute.

A research team led by the University of Washington recently reported that carefully constructed stacks of graphene can exhibit highly correlated electron properties. The team also found evidence that this type of collective behavior likely relates to the emergence of exotic magnetic states.

We’ve created an experimental setup that allows us to manipulate electrons in the graphene layers in a number of exciting new ways, said co-senior author Matthew Yankowitz, a UW assistant professor of physics and of materials science and engineering. Yankowitz led the team with co-senior author Xiaodong Xu, a UW professor of physics and of materials science and engineering.

Scientists at EPFL have recently published a research that could open up new pathways to boosting the capacity of sodium-ion batteries. Lithium is becoming a critical material as it is used extensively in cell-phones and car batteries, while, in principle, sodium could be a much cheaper, more abundant alternative, says Ferenc Simon, a visiting scientist in the group of László Forró at EPFL. This motivated our quest for a new battery architecture: sodium doped graphene.

Since sodium is far more abundant than lithium, and the risk of fire is much lower with this battery chemistry, it is considered a potentially viable replacement to current lithium-ion technology. But sodium also has much lower energy density than lithium, which has so far limited uptake, particularly in the electric vehicle and consumer electronics segments, where the physical size of the battery is a deciding factor. EPFL's new work uses graphene to address this issue.

A team of researchers at Princeton has looked for the origins of the unusual behavior known as magic-angle twisted bilayer graphene, and detected signatures of a cascade of energy transitions that could help explain how superconductivity arises in this material.

"This study shows that the electrons in magic-angle graphene are in a highly correlated state even before the material becomes superconducting, "said Ali Yazdani, Professor of Physics and the leader of the team that made the discovery. "The sudden shift of energies when we add or remove an electron in this experiment provides a direct measurement of the strength of the interaction between the electrons."

The Graphene Flagship has announced 16 New FLAG-ERA projects, that cover a broad range of topics, from fundamental to applied research. These projects which will become Partnering Projects of the Graphene Flagship receiving around €11 million in funding overall.

Bringing together a diverse range of European knowledge and expertise, FLAG-ERA is an ERA-NET (European Research Area Network) initiative that aims to create synergies between new research projects and the Graphene Flagship and Human Brain Project.

An international group of Russian and Japanese scientists recently developed a graphene-based material that might significantly increase the recording density in data storage devices, such as SSDs and flash drives. Among the main advantages of the material is the absence of rewrite limit, which will allow implementing new devices for Big Data processes.

The development of compact and reliable memory devices is an increasing need. Today, traditional devices are devices in which information is transferred through electric current. The simplest example is a flash card or SSD. At the same time, users inevitably encounter problems: the file may not be recorded correctly, the computer may stop "seeing" the flash drive, and to record a large amount of information, rather massive devices are required.

Graphene, despite its excellent mechanical, electronic and optical properties, is traditionally not deemed suitable for magnetic applications. Swiss Federal Laboratories for Materials Science and Technology (EMPA) Researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronics applications.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties. Together with colleagues from the Technical University in Dresden, Aalto University in Finland, Max Planck Institute for Polymer Research in Mainz and University of Bern, Empa researchers have succeeded in building a nanographene with magnetic properties that could be a decisive component for spin-based electronics functioning at room temperature.

Physicists from the University of Groningen constructed a two-dimensional spin transistor, in which spin currents were generated by an electric current through graphene. A monolayer of a transition metal dichalcogenide (TMD) was placed on top of the graphene to induce charge-to-spin conversion in the graphene.

Spintronics is an attractive alternative way of creating low-power electronic devices. It is not based on a charge current but rather on a current of electron spins. Spin is a quantum mechanical property of an electron, a magnetic moment that could be used to transfer or store information.