Stanford team finds novel form of magnetism in twisted bi-layer graphene

Stanford physicists recently observed a novel form of magnetism, predicted but never seen before, that is generated when two graphene sheets are carefully stacked and rotated to a special angle. The researchers suggest the magnetism, called orbital ferromagnetism, could prove useful for certain applications, such as quantum computing.

bi-layer graphene between hBN gives off orbital ferromagnetism imageOptical micrograph of the assembled stacked structure, which consists of two graphene sheets sandwiched between two protective layers made of hexagonal boron nitride. (Image: Aaron Sharpe)

“We were not aiming for magnetism. We found what may be the most exciting thing in my career to date through partially targeted and partially accidental exploration,” said study leader David Goldhaber-Gordon, a professor of physics at Stanford’s School of Humanities and Sciences. “Our discovery shows that the most interesting things turn out to be surprises sometimes.”

MIT team uses wax to smooth out wrinkles in graphene

Researchers at MIT have utilized an everyday material - wax- to protect graphene from performance-impairing wrinkles and contaminants. Removing graphene from the substrate it’s grown on and transferring it to a new substrate is known t be challenging. Traditional methods encase the graphene in a polymer that protects against breakage but also introduces defects and particles onto graphene’s surface. These interrupt electrical flow and stifle performance.

MIT process for smoothing out graphene wrinkles with wax imagea Schematics showing the process of paraffin-assisted graphene transfer. b Schematics showing the effect of paraffin’s thermal expansion on graphene wrinkle. c A typical paraffin-supported graphene film floated on water at different temperatures

The MIT team describes a fabrication technique that applies a wax coating to a graphene sheet and heats it up. Heat causes the wax to expand, which smooths out the graphene to reduce wrinkles. Moreover, the coating can be washed away without leaving behind much residue.

Researchers provide a new twist on graphene's superconductivity

A team of researchers led by Columbia University have developed a new method to finely tune adjacent layers of graphene, in a research that provides new insights into the physics underlying the material's intriguing characteristics.

Researchers provide a new twist on graphene's superconductivity image

"Our work demonstrates new ways to induce superconductivity in twisted bilayer graphene, in particular, achieved by applying pressure," said Cory Dean, assistant professor of physics at Columbia and the study's principal investigator. "It also provides critical first confirmation of last year's MIT results - that bilayer graphene can exhibit electronic properties when twisted at an angle - and furthers our understanding of the system, which is extremely important for this new field of research".

Researchers catalog graphene defects

Researchers at MIT have produced a catalog of the exact sizes and shapes of defects and holes that would most likely be observed (as opposed to the many more that are theoretically possible) when a given number of atoms is removed from the atomic lattice. The MIT team collaborated on this project with researchers at Lockheed Martin Space and Oxford University.

MIT develops graphene defects catalog imageThe 12 different forms that six-atom vacancy defects in graphene can have, as determined by the researchers

“It’s been a longstanding problem in the graphene field, what we call the isomer cataloging problem for nanopores,” Michael Strano from MIT says. "For those who want to use graphene or similar two-dimensional, sheet-like materials for applications including chemical separation or filtration", he says, “we just need to understand the kinds of atomic defects that can occur,” compared to the vastly larger number that are never seen".

Army research shows how graphene oxide can help improve munitions

Researchers from the U.S. Army, in collaboration with RDECOM Research Laboratory, the Army's corporate research laboratory (ARL), Stanford University, MIT, University of Southern California and Argonne National Laboratory, have discovered a way to get more energy out of energetic materials containing aluminum, common in battlefield systems, by igniting aluminum micron powders coated with graphene oxide. This research could lead to enhanced energetic performance of metal powders as propellant/explosive ingredients in Army's munitions.

GO for better munitions image

This discovery makes use of graphene oxide as an effective light-weight additive for practical energetic applications using micron-size aluminum powders (µAl), i.e., aluminum particles one millionth of a meter in diameter.

Versarien - Think you know graphene? Think again! Versarien - Think you know graphene? Think again!