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.”

Graphene enables researchers to control infrared and terahertz waves

Researchers from the University of Geneva (UNIGE) in Switzerland and the University of Manchester in the UK have found an efficient way to control infrared and terahertz waves using graphene. "There exist a class of the so-called Dirac materials, where the electrons behave as if they do not have a mass, similar to light particles, the photons," explains Alexey Kuzmenko, a researcher at the Department of Quantum Matter Physics in UNIGE's Science Faculty, who co-conducted this research together with Ievgeniia Nedoliuk.

The interaction between graphene and light suggests that this material could be used to control infrared and terahertz waves. "That would be a huge step forward for optoelectronics, security, telecommunications and medical diagnostics," points out the Switzerland-based researcher.

Unique device that combines graphene and boron nitride can switch from superconducting to insulating

Researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a graphene device that switches from a superconducting material to an insulator and back again to a superconductor — all with a flip of a switch. The team shared that the device exhibits this unique versatility while being thinner than a human hair.

Graphene and hBN device moves from insulating to superconducting imageViews of the trilayer graphene/boron nitride heterostructure device as seen through an optical microscope. The gold, nanofabricated electric contacts are shown in yellow; the silicon dioxide/silicon substrate is shown in brown and the boron nitride flakes

"Usually, when someone wants to study how electrons interact with each other in a superconducting quantum phase versus an insulating phase, they would need to look at different materials. With our system, you can study both the superconductivity phase and the insulating phase in one place," said Guorui Chen, the study's lead author and a postdoctoral researcher in the lab of Feng Wang, who led the study. Wang, a faculty scientist in Berkeley Lab's Materials Sciences Division, is also a UC Berkeley physics professor.

Researchers develop washable, wearable graphene capacitors that can be woven directly into clothes

Researchers at the University of Cambridge and Jiangnan University in China have developed graphene-enhanced wearable electronic components incorporated directly into fabrics. The devices could be used for flexible circuits, healthcare monitoring, energy conversion, and other applications.

The researchers have shown how graphene and other related materials can be directly incorporated into fabrics to produce charge storage elements such as capacitors, paving the way to textile-based power supplies which are washable, flexible and comfortable to wear.

Graphene quantum dots to help create single electron transistors

Scientists from Manchester University, the Ulsan National Institute of Science & Technology and the Korea Institute of Science and Technology have developed a novel technology, which combines the fabrication procedures of planar and vertical heterostructures in order to assemble graphene-based single-electron transistors.

Graphene quantum dots to help create single electron transistorsThe schematic structure of the devices

In the study, it was demonstrated that high-quality graphene quantum dots (GQDs), regardless of whether they were ordered or randomly distributed, could be successfully synthesized in a matrix of monolayer hexagonal boron nitride (hBN). Here, the growth of GQDs within the layer of hBN was shown to be catalytically supported by the platinum (Pt) nanoparticles distributed in-between the hBN and supporting oxidised silicon (SiO2) wafer, when the whole structure was treated by the heat in the methane gas (CH4). It was also shown, that due to the same lattice structure (hexagonal) and small lattice mismatch (~1.5%) of graphene and hBN, graphene islands grow in the hBN with passivated edge states, thereby giving rise to the formation of defect-less quantum dots embedded in the hBN monolayer.