Boron Nitride - Page 4

Researchers at the University of Basel in Switzerland, Budapest University of Technology and Economics in Hungary and National Institute for Material Science in Japan have developed a new, super-small device that is capable of detecting minute magnetic fields.

A conventional SQUID (left) and the new SQUID (right). (University of Basel, Department of Physics)

The device, a new kind of superconducting quantum interference device (SQUID), is just 10 nanometres high, or around a thousandth of the thickness of a human hair. It's made from two layers of graphene making it one of the smallest SQUIDs ever built separated by a very thin layer of boron nitride.

Cornell researchers, led by Katja Nowack, assistant professor of physics, used an ultrathin graphene and hexagonal boron nitride 'sandwich' to create a tiny magnetic field sensor that can operate over a greater temperature range than previous sensors, while also detecting miniscule changes in magnetic fields that might otherwise get lost within a larger magnetic background.

Nowack's lab specializes in using scanning probes to conduct magnetic imaging. One of their go-to probes is the superconducting quantum interference device, or SQUID, which works well at low temperatures and in small magnetic fields.

Researchers at Delft University of Technology (TU Delft) recently presented what they say is the first mechanically-tunable monolayer graphene QD whose electronic properties can be modified by in-plane nanometer displacements.

The ability to precisely manipulate individual charge carriers can be considered as a cornerstone for single-electron transistors and for electronic devices of the future, including solid-state quantum bits (qubits). Quantum dots (QDs) are at the heart of these devices.

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.

Researchers at MIT are working to develop a graphene-based device that may be able to convert ambient terahertz waves into a direct current. The MIT team explains that any device that sends out a Wi-Fi signal also emits terahertz waves —electromagnetic waves with a frequency somewhere between microwaves and infrared light. These high-frequency radiation waves, known as T-rays, are also produced by almost anything that registers a temperature, including our own bodies and the inanimate objects around us.

Terahertz waves are pervasive in our daily lives, and if harnessed, their concentrated power could potentially serve as an alternate energy source. Imagine, for instance, a cellphone add-on that passively soaks up ambient T-rays and uses their energy to charge your phone. However, to date, terahertz waves are wasted energy, as there has been no practical way to capture and convert them into any usable form. This is exactly what the MIT scientists set out to do.

A collaborative group of scientists has designed a device that makes use of graphene’s assorted talents: superconducting, insulating, and a type of magnetism called ferromagnetism. The multitasking device could enable new physics experiments, such as research in the pursuit of an electric circuit for faster, next-generation electronics like quantum computing technologies.

An optical image of the graphene device (shown above as a square gold pad) on a silicon dioxide/silicon chip. Shining metal wires are connected to gold electrodes for electrical measurement. (Credit: Guorui Chen/Berkeley Lab)

So far, materials simultaneously showing superconducting, insulating, and magnetic properties have been very rare. And most people believed that it would be difficult to induce magnetism in graphene, because it’s typically not magnetic. Our graphene system is the first to combine all three properties in a single sample, said Guorui Chen, a postdoctoral researcher in Wang’s Ultrafast Nano-Optics Group at UC Berkeley, and the study’s lead author.

Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have used graphene and STM technology to create and image a novel pair of quantum dots — tiny islands of confined electric charge that act like interacting artificial atoms. Such coupled quantum dots could serve as a robust quantum bit, or qubit, the fundamental unit of information for a quantum computer. Moreover, the patterns of electric charge in the island can’t be fully explained by current models of quantum physics, offering an opportunity to investigate rich new physical phenomena in materials.

a system of coupled quantum dots taken by STM shows electrons orbiting within two concentric sets of rings, separated by a gap. The inner set of rings represents one quantum dot; the outer, brighter set represents a larger, outer quantum dot. Credit: NIST

The NIST -led team included researchers from the University of Maryland NanoCenter and the National Institute for Materials Science in Japan. The team used the ultrasharp tip of a scanning tunneling microscope (STM) as if it were a stylus of sorts. Hovering the tip above an ultracold sheet of graphene, the researchers briefly increased the voltage of the tip.

Researchers from Israel's Weizmann Institute and the UK's Manchester University have succeeded in imaging electrons' hydrodynamic flow pattern for the first time using a novel scanning probe technique. They have proven the longstanding scientific theory that electrons can behave like a viscous liquid as they travel through a conducting material, producing a spatial pattern that resembles water flowing through a pipe.

The results of this study could help developers of future electronic devices, especially those based on 2D materials like graphene in which electron hydrodynamics is important.

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.

Optical 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.

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.