Category Technology/Electronics

Schematic of a laser beam energizing a monolayer semiconductor made up of molybdenum disulfide (MoS2). The red glowing dots are particles excited by the laser. Credit: Der-Hsien Lien Read more at: http://phys.org/news/2015-11-defect-free-molecule-thick.html#jCp

An emerging class of atomically thin materials, monolayer semiconductors has generated a great deal of buzz in the world of materials science. Monolayers hold promise in the development of transparent LED displays, ultra-high efficiency solar cells, photo detectors and nanoscale transistors. Their downside? The films are notoriously riddled with defects, killing their performance.

But a UCLA, Berkeley, and Lawrence Berkeley National Lab team, has found a simple way to fix these defects via an organic superacid...

Left: Allowed states for the standard type-I Weyl fermion. When energy is tuned from below, at zero energy, a pinch in the number of allowed states guarantees the absence of many-body phenomena such as superconductivity or ordering. Right: The newly discovered type-II Weyl fermion. At zero energy, a large number of allowed states are still available. This allows for the presence of superconductivity, magnetism, and pair-density wave phenomena. Credit: B. Andrei Bernevig et al.

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials act as insulators for current applied in some directions and as conductors for current applied in other directions...

This is an example of an inkjet printed rainbow hologram. Credit: ITMO University

This new method is expected to significantly reduce the cost and time needed to create the so-called rainbow holograms, commonly used for security purposes – to protect valuable items, such as credit cards and paper currency, from piracy and falsification.

The team, led by Alexander Vinogradov, SCAMT in ITMO University, developed colorless ink made of nanocrystalline titania, which can be loaded into an inkjet printer and then deposited on special microembossed paper, resulting in unique patterned images. The ink makes it possible to print custom holographic images on transparent film in a matter of minutes, instead of days as with the use of conventional methods.

“The conventional way of preparing a rainbow ...

a) Maximum magnetic field Bc2 (normalized) at which superconductivity can survive versus temperature T. Filled circles are data taken from MoS2 thin films. Without taking into account internal magnetic fields generated by the lattice structure of MoS2, Bc2 cannot exceed 1. b) Taking into account the internal magnetic fields, the experimental data can be well explained theoretically. Credit: The Physics Department, HKUST

Superconductivity is a fascinating quantum phenomenon in which electrons form pairs and flow with 0 resistance. However, strong enough magnetic field can break electron pairs and destroy superconductivity. Surprisingly, experimental groups led by Prof. Ye and Prof...