Bhagwan's Science blog

An international team including researchers from The University of Tokyo Institute of Industrial Science has created particles with an off-center core or "eye" that can be tracked using microscopy. 

Particles suspended in a liquid move from one place to another as a result of Brownian motion, which can be easily detected with a microscope. However, these particles also rotate, which is much more difficult to see if they are spherical.

The researchers overcame this by creating particles made from two different colors of the same material. The core sphere—which they call the eye—is set off-center at the surface of the particle. It provides a point that can be followed under a microscope to determine the orientation changes as the particle rotates.

By tracking a dense suspension of charged particles forming a colloidal crystal—which has an ordered arrangement of particles—it was found that the rotation of neighboring spheres was coupled and moved in opposite directions, like meshed gears.

In addition, a system with uncharged particles showed that there was a relationship between local crystallinity—the ordering in the immediate surroundings—and the rotational diffusivity, which describes the process of the orientation regaining equilibrium.

The researchers also observed "stick-slip" rotational motion between particles that make contact, where a large neighbor could stop the motion of a particle through friction.

"We expect our findings to have a significant impact on the design of industrial processes involving colloids, as well as on the understanding of biological processes."

Source : Physical Review X, Phy.org

The future of quantum computing may depend on the further development and understanding of semiconductor materials known as transition metal dichalcogenides (TMDCs). These atomically thin materials develop unique and useful electrical, mechanical, and optical properties when they are manipulated by pressure, light, or temperature.

Engineers from Rensselaer Polytechnic Institute demonstrated how, when the TMDC materials they make are stacked in a particular geometry, the interaction that occurs between particles gives researchers more control over the devices' properties. Specifically, the interaction between electrons becomes so strong that they form a new structure known as a correlated insulating state. This is an important step, researchers said, toward developing quantum emitters needed for future quantum simulation and computing.

Much of the research has focused on gaining a better understanding of the potential of the exciton, which is formed when an electron, excited by light, bonds with a hole—a positively charged version of the electron. Shi and his team have demonstrated this phenomenon in TMDC devices made of layers of tungsten disulfide (WS2) and tungsten diselenide (WSe2). Recently, the team also observed the creation of an interlayer exciton, which is formed when an electron and hole exist in two different layers of material. The benefit of this type of exciton, Shi said, is that it holds a longer lifetime and responds more significantly to an electric field—giving researchers greater ability to manipulate its properties.

In their latest research, Shi and his team showed how, by stacking TMDCs in a particular manner, they can develop a lattice known as a moiré superlattice. Picture two sheets of paper stacked on top of one another, each with the same pattern of hexagons cut out of them. If you were to shift the angle of one of the pieces of paper, the hexagons would no longer perfectly match up. The new formation is similar to that of a moiré superlattice.

The benefit of such a geometry, Shi said, is that it encourages electrons and interlayer excitons to bond together, further increasing the amount of control researchers have over the excitons themselves. This discovery, Shi said, is an important step toward developing quantum emitters that will be needed for future quantum simulation and quantum computing.

"It has essentially opened the door to a new world. We see a lot of things already, just by peeking through the door, but we have no idea what is going to happen if we open the door and get inside," Shi said. "That is what we want to do, we want to open the door and get inside."

Source: Physics.org, Nature Communications

Google launches 'BOLO' app to tutor children to read in HINDI, ENGLISH.

Tech giant Google unveiled a new app 'Bolo' that aims to help children in primary school learn to read in Hindi and English.

-> The free app, which is being launched in India first, uses Google's speech recognition and text-to-speech technology.

-> The app features an animated character 'Diya' who encourages children to read stories aloud and helps if child is unable to pronounce a word.

-> It also lauds the reader when she completes the reading.