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Showing posts with label Electronics. Show all posts
Showing posts with label Electronics. Show all posts

Saturday, 8 February 2020

A new quasiparticle is discovered: Pi-ton

Two electrons and two gaps, conjugated by the injection of a photon, remain together, forming the quasiparticle ฮ -ton.


There are very different types of particles: Elementary particles are the fundamental blocks of matter. Atoms, for example, are "linked" - or associated - states that consist of several minor constituents, such as quarks.

And there are so-called "quasiparticles" - excitations in a system formed by many particles, but which behave together exactly as if they were a single particle.

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It is one of those complex particles - dubbed ฮ -ton - that was discovered by Anna Kauch and her colleagues at the Vienna University of Technology, Austria.

In addition to describing the behavior of Pi-ton in simulations, the team also indicated the way for experimentalists to detect it in the laboratory.


Quasiparticles

The simplest and most well-known quasiparticle is the Hole, the carrier of positive charge. When an electron, which carries the negative charge, moves, it leaves a Hole in its place. There doesn't seem to be anything concrete there - hence the name Hole - but that "absence of electron" behaves in many ways as if it were a particle.

However, unlike an electron, which can also be seen outside a crystal, the Hole exists only in conjunction with the other particles. It is for these and others thinhs that it is interpreted as a quasiparticle.

But there are more complex quasiparticles, such as excitons , that play a central role in semiconductor physics , at the basis of the functioning of various hardware components. Exciton is a bonded state of an electron and a Hole, which is created when light hits a material. Instead of the electron and the Hole annihilating, they form a bond, and that bonded state is a quasiparticle.


Sketch of the physical processes (top) and Feynman diagrams (bottom) behind an exciton (left) and a  ฯ€ -ton (right). The yellow wiggled line symbolizes the incoming (and outgoing) photon, which creates an electron-hole pair denoted by open and filled circles, respectively. The Coulomb interaction between the particles is symbolized by a red wiggled line; dashed line indicates the recombination of the particle and hole; dotted line denotes the creation of a second particle-hole pair (right); black lines the underlying band structure (top panels).


Pi-ton

Anna and her colleagues Petra Pudleiner and Katharina Astleithner were just studying the excitons when they realized that their calculations were showing something much broader than expected: electrons and Holes don't have to bond just in pairs.

In fact, the calculations showed the possibility that two electrons could bind to two Holes, forming an unprecedented quasiparticle: they called it Pi-ton, or ฮ -ton.

"The name pi-ton comes from the fact that the two electrons and the two Holes are held together by charge density fluctuations or spin fluctuations that always invert their character 180 degrees from one point in the crystalline network to the next - or that is, by an angle of pi, measured in radians, "said Anna.

"This constant shift from more to less can be imagined as a shift from black to white on a chessboard," illustrated Petra.

Like exonium, pi-ton is created spontaneously when the material absorbs a photon. When the quasiparticle falls apart, a photon is emitted again.



"Although we are constantly surrounded by countless quasiparticles, the discovery of a new species of quasiparticle is something very special. In addition to exxciton, now there is also pi-ton. Anyway, this contributes to a better understanding of the coupling between light and solids. , a topic that plays an important role not only in basic research, but also in many technical applications - from semiconductor technology to photovoltaic energy," said Professor Karsten Held.


Bibliography:

Article: Generic Optical Excitations of Correlated Systems: ฯ€-tons

Authors: Anna Kauch, Petra Pudleiner, Katharina Astleithner, P. Thunstrรถm, T. Ribic, Karsten Held

Magazine: Physical Review Letters

Vol .: 124, 047401

DOI: 10.1103 / PhysRevLett.124.047401

Wednesday, 18 December 2019

Smart contact lens recharges wirelessly without removing it from user's eye


Electronic Contact Lenses

The robotic contact lenses have promised true superpowers to humans, the vision of laser beams to a telescopic zoom built into the eye.

This technology, still in the developmental stage, has now received a huge boost: a wireless rechargeable power source, meaning all equipment installed on the contact lens can be fueled and continue working without even being removed from the user's eye.

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Instead of a traditional battery, Jihun Park and colleagues at Yonsei University in South Korea used a printable supercapacitor, making it easy to attach to the contact lens.

In addition to the rechargeable supercapacitor, the prototype has an antenna and a red LED, all working without obscuring the user's vision. It sounds like science fiction, but the device has already been tested by a volunteer and worked perfectly.

Wireless rechargeable supercapacitor scheme.

Rechargeable supercapacitor

The supercapacitor is made of carbon electrodes and a solid state polymer electrolyte. Each material is dispersed in a solvent and printed as separate layers on the lens. A high-precision technique called microscale direct ink writing allows the supercapacitor to be printed outside the area covering the user's pupil, meaning that the device does not interfere with vision.

The flexible wireless power transfer unit - comprising an ultra-thin rectifier circuit and an antenna made of nanofibers and silver nanowires - allows the contact lens to recharge at a distance of about 1 cm from a transmitting coil.



The rechargeable contact lens was tested on live rabbits and finally on a human - during the 10 minute test, no damage was detected in the volunteer's eye.


Bibliography:

Article: Printing of wirelessly rechargeable solid-state supercapacitors for soft, smart contact lenses with continuous operations

Authors: Jihun Park, David B. Ahn, Joohee Kim, Byeong-Soo Bae, Sang-Young Lee, Jang-Ung Park

Magazine: Science Advances

Vol .: 5, no. 12, eaay0764
DOI: 10.1126 / sciadv.aay0764

Tuesday, 17 December 2019

Magnonica promises 1,000 times faster processors - and no overheat

Future devices like this one, based on magnet torque, will be faster, consume less power and will not overheat.

Magnetic wave computing

Singapore researchers have developed a revolutionary way to encode computational information without using electric current.

This will allow you to build faster appliances that can use energy efficiently without overheating, as well as more energy efficient logic and memory devices.

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Instead of adopting the traditional electron injection methods used in traditional electronics, Yi Wang and his colleagues used "spin waves" to toggle bit magnetization.

Spin waves are propagations of disturbances in the crystal structure of magnetic materials. These waves are typically described as quasiparticles, known as " magnons ", and establish a kind of link between "electro" and "magnetism" . Just as the spin of electrons gave rise to spintronics , it was long hoped that magnons could be explored technologically, creating a magnetic.



In addition to everything operating at room temperature, the operating frequency of spin waves is in the terahertz range, at least a thousand times faster than the gigahertz of today's processors. Terahertz devices will be able to transmit data at significantly higher speeds than currently possible.

Comparison between the operation of one component based on electron spin (spintronic) and another based on magnetic (magnetic) spin.

Magnetic

The team built a two-layer component consisting of an antiferromagnetic magnet transport channel and a spin source in the form of a topological insulator . In an unprecedented feat, they successfully demonstrated the switching of one-bit spin-wave magnetization in the ferromagnetic layer with high efficiency.

The new spin-erase bit-based switching scheme relies on the moving charges of electrons. Therefore, circuits using this mechanism should have significantly lower Joule power and heat dissipation than equivalent electronics - in simpler terms, processors that don't heat up and use very little energy, allowing a new wave of speed up in computing. and portable devices with much longer batteries.

"Spin waves (magnons) can transmit information even on insulating [materials] without involving moving loads. This unique property allows for longer spin propagation but less dissipation compared to electron spins.

"Then we can control the magnetization if we transfer the spin information from the magnons to the local magnetization, which can be understood as a 'magnet torque'. Just as a linear force is an impulse or a traction, a torque can be considered as a Thus, this new way of manipulating magnetization can be used for future logic and memory devices.



"We know that electric spin torque has opened the era for applications of spintronic devices such as random access magnetic memories (MRAMs). We believe that our description of the new magnetization torque scheme for magnetization switching is a revolutionary idea in spintronics. "It will reinvigorate not only a new area of ​​research in magnetic, but also practical, magnon-operated devices," said Wang Yi of the National University of Singapore.

Next, the team plans to work to further increase the efficiency of the magnet torques and start building the various magnetic components that can have the same functionality as the electronics, but without involving any electrical parts.


Bibliography:

Article: Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator

Authors: Yi Wang, Dapeng Zhu, Yumeng Yang, Kyusup Lee, Rahul Mishra, Gyungchoon Go, Se-Hyeok Oh, Dong-Hyun Kim, Kaiming Cai, Enlong Liu, Shawn D. Pollard, Shuyuan Shi, Jongmin Lee, Kie Leong Teo, Yihong Wu, Kyung-Jin Lee, Hyunsoo Yang

Journal: Science

Vol .: 366, Issue 6469, pp. 1125-1128
DOI: 10.1126 / science.aav8076

Friday, 13 December 2019

Liquid crystal microlenses capture 4D images

The polarization of light brings a new world of information.

4D images

While most images captured by a camera lens are still flat and two-dimensional, more and more 3D imaging technologies are providing the crucial depth context for medical and scientific applications.

An additional step is in 4D images, whose additional dimension refers to information about light polarization.

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This may open even more application possibilities, but the first prototypes of this technology, such as a 4D microscope , consist of bulky, expensive and complicated equipment.

Now researchers at Nanjing University in China have developed liquid crystal microlenses that can reveal 4D information in a single photographic shot.

The microlenses do not have to be "fabricated" - they assemble themselves thanks to the liquid crystal.

Polarized light

Polarized light contains waves that oscillate in a single plane, while unpolarized light, such as that of the sun, contains waves that move in all directions. Light can become polarized upon reflection of objects, and detecting such light can reveal information that is not available just by looking at the object - for example, cancer cells may reflect polarized light differently from healthy tissues.

Ling-Ling Ma and his colleagues wanted to develop a portable, inexpensive, easy-to-use microlens to simultaneously capture 3D space information plus polarization producing 4D images.

They succeeded using liquid crystals. With a self-assembly process, they modeled microlens arrays in concentric circles, creating a new type of flat lens .

Microlenses capture light reflected by the object differently depending on the distance from the object (depth) and the direction of polarized light, producing 4D information in a single shot.



Although the resolution still needs to be improved, the technique could be used for medical imaging, telecommunications, screens and monitors, remote sensing and even encryption, the researchers say.


Bibliography:

Article: Self-Assembled Asymmetric microlenses for Four-Dimensional Visual Imaging

Authors: Ling-Ling Ma Sai-Bo Wu, Wei Hu, Chao Liu, Peng Chen, Hao Qian, Yandong Wang Lifeng Chi, Yan-qing Lu

Magazine : ACS Nano

DOI: 10.1021 / acsnano.9b07104

Saturday, 23 November 2019

Structured light allows communication with infinite Photonic alphabet

Illustration shows the creation of hybrid interlaced photons combining polarization with a twisted light pattern that carries orbital angular momentum . This structured light allows you to use quantum protocols to create a larger coding alphabet, more security and better noise resistance.


Structured light

The creation of Structured Light beams - light in exotic patterns such as spirals - not only revealed a strange new world of light, but also opened new fields of technological exploration for photonics .

And it seems that these application possibilities have not even been scratched.

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Two South African researchers have already shown that it is possible to exploit helical beams of light to create an alphabet, which promises not only greater security and robustness in communications, but also a new way to explore the physics behind quantum computers. .

"What we really want is to do quantum mechanics with light patterns. By that we mean that light comes in a variety of patterns that can be differentiated - like our faces," explained Andrew Forbes of the University of Witwatersrand.


Since light patterns can be distinguished from each other, they can be used as an alphabet form. "The cool thing is that there is, at least in principle, an infinite set of patterns, so an infinite alphabet is available," said Forbes.

Different patterns of structured light - the "letters" of the infinite photonic alphabet.

Multidimensional States

Traditionally, quantum protocols have been implemented with light bias, which has only two values, which means a maximum photon information capacity of just 1 bit - remembering that one bit per photon is already incredibly better than the floods of light. electrons used today. Using structured light patterns as an alphabet, in turn, the information capacity is much greater, not to mention the gains in safety and noise resistance.

"Light patterns are a path to what we call large states," continues Forbes. "They are large because many standards are involved in the quantum process. Unfortunately, the toolkit for managing these patterns is still underdeveloped and requires a lot of work."

That's why he and his colleague Isaac Nape began working with hybrid states, which combine the traditional use of polarization with structured modes of light.

"It turns out that many protocols can be implemented efficiently with simpler tools, combining polarized patterns for the best of both worlds," said Forbes. "Instead of two pattern dimensions, hybrid states allow access to multidimensional states, for example an infinite set of two-dimensional systems. This seems to be a promising way to truly make a quantum lattice based on light patterns come true."




Bibliography:

Article: Quantum mechanics with patterns of light: Progress in high dimensional and multidimensional entanglement with structured light

Authors: Andrew Forbes, Isaac Nape

Magazine: AVS Quantum Science

DOI: 10.1116 / 1.5112027

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