Fundamental research sheds light on new many-particle quantum physics in atomically thin semiconductors
A paper published in Nature Communications by Sufei Shi, assistant professor of chemical and biological engineering at Rensselaer, increases our understanding of how light interacts with atomically thin semiconductors and creates unique excitonic complex particles, multiple electrons, and holes strongly bound together. These particles possess a new quantum degree of freedom, called “valley spin.” The “valley spin” is similar to the spin of electrons, which has been extensively used in information storage such as hard drives and is also a promising candidate for quantum computing.
The paper, titled “Revealing the biexciton and trion-exciton complexes in BN encapsulated WSe2,” was published in the Sept. 13, 2018, edition of Nature Communications. Results of this research could lead to novel applications in electronic and optoelectronic devices, such as solar energy harvesting, new types of lasers, and quantum sensing.
Shi’s research focuses on low dimensional quantum materials and their quantum effects, with a particular interest in materials with strong light-matter interactions. These materials include graphene, transitional metal dichacogenides (TMDs), such as tungsten diselenide (WSe2), and topological insulators.
Novel materials can considerably improve storage capacity and cycling stability of rechargeable batteries. Among these materials are high-entropy oxides (HEO), whose stability results from a disordered distribution of the elements. With HEO, electrochemical properties can be tailored, as was found by scientists of the team of nanotechnology expert Horst Hahn at Karlsruhe Institute of Technology (KIT). The researchers report their findings in the journal Nature Communications.
Sustainable energy supply requires reliable storage systems. Demand for rechargeable electrochemical energy storage devices for both stationary and mobile applications has increased rapidly in the past years and is expected to continue to grow in the future. Among the most important properties of batteries are their storage capacity and their cycling stability, i.e. the number of possible charging and discharging processes without any loss of capacity. Thanks to its high stability, an entirely new class of materials called high-entropy oxides (HEO) is expected to result in major improvements. Moreover, electrochemical properties of HEO can be customized by varying their compositions. For the first time, scientists of KIT’s Institute of Nanotechnology (INT) and Karlsruhe Nano Micro Facility (KNMF), of the Helmholtz Institute Ulm (HIU) established jointly by KIT and Ulm University, and of the Indian Institute of Technology in Madras have now demonstrated the suitability of HEO as conversion materials for reversible lithium storage. Conversion batteries based on electrochemical material conversion allow for an increase of the stored amount of energy, while battery weight is reduced. The scientists used HEO to produce conversion-based electrodes that survived more than 500 charging cycles without any significant degradation of capacity.
Why LG Chem Leads In Electric-Car Batteries: Materials Science, It Says:
The top three battery makers for electric cars today are Panasonic, AESC, and LG Chem. But while Panasonic sells largely to Tesla, and AESC is a joint venture half-owned by Nissan, LG sells its cells to more carmakers than any other battery company. And the secret to that success is LG’s expertise in chemicals and materials science, according to… http://dlvr.it/9sVkXH
In every modern microcircuit hidden inside a laptop or smartphone, you can see transistors—small semiconductor devices that control the flow of electric current, i.e. the flow of electrons. If we replace electrons with photons (elementary particles of light), then scientists will have the prospect of creating new computing systems that can process massive information flows at a speed close to the speed of light. At present, it is photons that are considered the best for transmitting information in quantum computers. These are still hypothetical computers that live according to the laws of the quantum world and are able to solve some problems more efficiently than the most powerful supercomputers.
Although there are no fundamental limits for creating quantum computers, scientists still have not chosen what material platform will be the most convenient and effective for implementing the idea of a quantum computer. Superconducting circuits, cold atoms, ions, defects in diamond and other systems now compete for being one chosen for the future quantum computer. It has become possible to put forward the semiconductor platform and two-dimensional crystals, specifically, thanks to scientists from: the University of Würzburg (Germany); the University of Southampton (United Kingdom); the University of Grenoble Alpes (France); the University of Arizona (USA); the Westlake university (China), the Ioffe Physical Technical Institute of the Russian Academy of Sciences; and St Petersburg University.
Illumination consumes more than 20 percent of electricity. Thus, finding an efficient, stable, single-phase warm white-light material is very important. Lead hybrid perovskites have drawn interest for excellent photoelectric performance and simple synthesis. Lead perovskites with white-light emission have been studied, but photoluminescence quantum efficiencies (PLQEs) are low. However, the large-scale application of lead perovskites is hindered by toxicity and instability. Therefore, the substitution of Pb with less toxic or non-toxic elements and the replacement of organic cations with relatively stable inorganic cations is being investigated.
Very recently, Keli Han’s group at the State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, reports a series of bulk lead-free double perovskites: Cs2AgBi1-xInxCl6 (0 < x < 1). They demonstrate the existence of the parity-forbidden transition by photophysical characterization in Cs2AgInCl6 bulk crystal. The Cs2AgBi0.125In0.875Cl6 breaks the parity-forbidden transition and shows warm white-light emission with broad emission across the entire visible spectrum, with the highest PLQE of 70.3%.
Imagine windows that can easily transform into mirrors, or super high-speed computers that run not on electrons but light. These are just some of the potential applications that could one day emerge from optical engineering, the practice of using lasers to rapidly and temporarily change the properties of materials.
“These tools could let you transform the electronic properties of materials at the flick of a light switch,” says Caltech Professor of Physics David Hsieh. “But the technologies have been limited by the problem of the lasers creating too much heat in the materials.”
In a new study in Nature, Hsieh and his team, including lead author and graduate student Junyi Shan, report success at using lasers to dramatically sculpt the properties of materials without the production of any excess damaging heat.
“The lasers required for these experiments are very powerful so it’s hard to not heat up and damage the materials,” says Shan. “On the one hand, we want the material to be subjected to very intense laser light. On the other hand, we don’t want the material to absorb any of that light at all.” To get around this the team found a “sweet spot,” Shan says, where the frequency of the laser is fine-tuned in such a way to markedly change the material’s properties without imparting any unwanted heat.
Prof. Ye Jichun’s team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), collaborating with researchers at the University of Nottingham Ningbo China, has revealed the underlying dynamics of Silicon oxide (SiOx) tunneling junctions, including pinhole formation processes and charge-carrier transport mechanisms. The study was published in Cell Reports Physical Science.
As one of the most promising alternatives to reduce the cost and improve the efficiency of devices, tunnel oxide passivating contact (TOPCon) technology has attracted considerable attention in the photovoltaic (PV) community. However, the physical mechanism of the core structures of TOPCon, i.e., polycrystalline silicon (poly-Si)/ SiOx/ crystalline silicon (c-Si) junctions, has not been clarified, restricting the further improvement of device efficiency.
To address this problem, researchers at NIMTE conducted extensive experiments and simulations, unraveling the underlying charge carrier dynamics of the SiOx tunneling junctions.
A new device being developed by Washington State University physicist Yi Gu could one day turn the heat generated by a wide array of electronics into a usable fuel source.
The device is a multicomponent, multilayered composite material called a van der Waals Schottky diode. It converts heat into electricity up to three times more efficiently than silicon – a semiconductor material widely used in the electronics industry. While still in an early stage of development, the new diode could eventually provide an extra source of power for everything from smartphones to automobiles.
“The ability of our diode to convert heat into electricity is very large compared to other bulk materials currently used in electronics,” said Gu, an associate professor in WSU’s Department of Physics and Astronomy. “In the future, one layer could be attached to something hot like a car exhaust or a computer motor and another to a surface at room temperature. The diode would then use the heat differential between the two surfaces to create an electric current that could be stored in a battery and used when needed.”
Gu recently published a paper on the Schottky diode in The Journal of Physical Chemistry Letters.
Members of the D. V. Skobeltsyn Institute of Nuclear Physic and colleagues from the Faculty of Chemistry of the Lomonosov Moscow State University have developed a new silicon- and germanium-based material that could significantly increase specific characteristics of lithium-ion batteries. The research results have been published in the Journal of Materials Chemistry A.
Lithium-ion batteries are the most popular type of energy storage system for modern electronic devices. They are composed of two electrodes—the negative (anode) and positive (cathode) ones, which are placed into a hermetic enclosure. The space in between is filled with a porous separator, steeped in a lithium ion-conductive electrolyte solution. The separator prevents short circuits between the bipolar electrodes and provides electrolyte volume, necessary for ion transport. Electric current in an external circuit is generated when lithium ions extract from the anode material and move through the electrolyte with further insertion into cathode material. However, the specific capacity of a lithium-ion battery is largely defined by the number of lithium ions that can be accepted and transferred by active materials of the anode and cathode.
The scientists have developed and studied a new anode material that allows energy efficiency of Li-ion batteries to be significantly increased. The material is suitable for utilization in both bulk and thin film Li-ion batteries.
Silicon – the second most abundant element in the earth’s crust – shows great promise in Li-ion batteries, according to new research from the University of Eastern Finland. By replacing graphite anodes with silicon, it is possible to quadruple anode capacity.
In a climate-neutral society, renewable and emission-free sources of energy, such as wind and solar power, will become increasingly widespread. The supply of energy from these sources, however, is intermittent, and technological solutions are needed to safeguard the availability of energy also when it’s not sunny or windy. Furthermore, the transition to emission-free energy forms in transportation requires specific solutions for energy storage, and lithium-ion batteries are considered to have the best potential.
Researchers from the University of Eastern Finland introduced new technology to Li-ion batteries by replacing graphite used in anodes by silicon. The study analysed the suitability of electrochemically produced nanoporous silicon for Li-ion batteries. It is generally understood that in order for silicon to work in batteries, nanoparticles are required, and this brings its own challenges to the production, price and safety of the material. However, one of the main findings of the study was that particles sized between 10 and 20 micrometres and with the right porosity were in fact the most suitable ones to be used in batteries. The discovery is significant, as micrometre-sized particles are easier and safer to process than nanoparticles. This is also important from the viewpoint of battery material recyclability, among other things. The findings were published in Scientific Reports.
Scientists at the U.S. Department of Energy’s Ames Laboratory were able to successfully manipulate the electronic structure of graphene, which may enable the fabrication of graphene transistors— faster and more reliable than existing silicon-based transistors.
The researchers were able to theoretically calculate the mechanism by which graphene’s electronic band structure could be modified with metal atoms. The work will guide experimentally the use of the effect in layers of graphene with rare-earth metal ions “sandwiched” (or intercalated) between graphene and its silicon carbide substrate. Because the metal atoms are magnetic the additions can also modify the use of graphene for spintronics.
“We are discovering new and more useful versions of graphene,” said Ames Laboratory senior scientist Michael C. Tringides. “We found that the placement of the rare earth metals below graphene, and precisely where they are located, in the layers between graphene and its substrate, is critical to manipulating the bands and tune the band gap.”
Physicists at UC San Diego have developed a new way to control the transport of electrical currents through high-temperature superconductors—materials discovered nearly 30 years ago that lose all resistance to electricity at commercially attainable low temperatures.
Their achievement, detailed in two separate scientific publications, paves the way for the development of sophisticated electronic devices capable of allowing scientists or clinicians to non-invasively measure the tiny magnetic fields in the heart or brain, and improve satellite communications.
“We believe this new approach will have a significant and far-reaching impact in medicine, physics, materials science and satellite communications,” said Robert Dynes, a professor of physics and former Chancellor of UC San Diego.
Ref: YBa2Cu3O7− δ superconducting quantum interference devices with metallic to insulating barriers written with a focused helium ion beam. Applied Physics Letters (2015) | http://dx.doi.org/10.1063/1.4922640
Researchers at the Department of Energy’s Oak Ridge National Laboratory have developed a new method to manipulate a wide range of materials and their behavior using only a handful of helium ions.
The team’s technique, published in Physical Review Letters, advances the understanding and use of complex oxide materials that boast unusual properties such as superconductivity and colossal magnetoresistance but are notoriously difficult to control.
For the first time, ORNL researchers have discovered a simple way to control the elongation of a crystalline material along a single direction without changing the length along the other directions or damaging the crystalline structure. This is accomplished by adding a few helium ions into a complex oxide material and provides a never before possible level of control over magnetic and electronic properties.
“By putting a little helium into the material, we’re able to control strain along a single axis,” said ORNL’s Zac Ward, who led the team’s study. “This type of control wasn’t possible before, and it allows you to tune material properties with a finesse that we haven’t previously had access to.”
Researchers at Chalmers Univ. of Technology have discovered that large area graphene is able to preserve electron spin over an extended period, and communicate it over greater distances than had previously been known. This has opened the door for the development of spintronics, with an aim to manufacturing faster and more energy-efficient memory and processors in computers.
Nano-sized diamonds with certain defects are assetsfor people who study light.
Marko Loncar, an NSF-funded electrical engineer at Harvard School of Engineering and Applied Sciences, creates tiny structures out of diamonds and other elements to manipulate how light and matter interact on the nanoscale.
For instance, Loncar, who is part of the Nanoscale Interdisciplinary Research Team, uses diamond posts in a silver substrate as the scalable platform to enhance single photon emission by nitrogen vacancy centers in diamond.
Nitrogen vacancy centers are defects formed in diamonds that allow for the precise manipulation of absorbed photons and emitted light.
You may not want a flawed diamond on your finger, but it’s the defect that makes things like quantum computing possible.
For electric vehicles (EVs) to become mainstream, they need cost-effective, safer, longer-lasting batteries that won’t explode during use or harm the environment. Researchers at the Georgia Institute of Technology may have found a promising alternative to conventional lithium-ion batteries made from a common material: rubber.
Elastomers, or synthetic rubbers, are widely used in consumer products and advanced technologies such as wearable electronics and soft robotics because of their superior mechanical properties. The researchers found that the material, when formulated into a 3D structure, acted as a superhighway for fast lithium-ion transport with superior mechanical toughness, resulting in longer charging batteries that can go farther. The research, conducted in collaboration with the Korea Advanced Institute of Science and Technology, was published Wednesday in the journal Nature.
An exotic material called gallium nitride (GaN) is poised to become the next semiconductor for power electronics, enabling much higher efficiency than silicon. In 2013, the Department of Energy (DOE) dedicated approximately half of a $140 million research institute for power electronics to GaN…
https://www.youtube.com/watch?v=hc7BSIbGDgw International Business Times (IBT) looks forward to CES 2016 and tells us what to expect from the consumer electronics show. From International Business Times Wearables are one of the most talked-about technology categories of the last couple of years
Yes, another gold audio fuse but this one has a pink LED and a bit more embellishment - four struts connected to two bracket rings. It does remind me of an old valve. It has very thin gold plate on the caps and central fuse - apparently it doesn’t degrade which effects sound quality in high end audio equipment. On this one I used a pink LED. The photo does make it look more purple but in reality it is more pink. I don’t like altering product photos too much.
As you can see the light is on when the post is inserted into the silver battery pack. The batteries can be replaced by screwing the top off. When I build these it’s so exciting turning it on for the first time - I was thrilled when I saw this one light up. Perfect for that theatrical costume or just that night out. It will certainly grab attention.
The top three battery makers for electric cars today are Panasonic, AESC, and LG Chem. But while Panasonic sells largely to Tesla, and AESC is a joint venture half-owned by Nissan, LG sells its cells to more carmakers than any other battery company. And the secret to that success is LG’s expertise in chemicals and materials science, according to… http://dlvr.it/9sVkXH
