(Kazan Federal University) While studying strontium titanate with electron paramagnetic resonance, a team from KFU's Center for Quantum Technology has found that the shape of a specimen of strontium titanate influences its internal symmetry. The research was co-conducted by the Ioffe Institute of Physics and Technology (Russia) and the Institute of Physics of the Czech Academy of Sciences.
(Forschungsverbund Berlin) Researchers from the Paul-Drude-Institut in Berlin, the Helmholtz-Zentrum in Dresden and the Ioffe Institute in St. Petersburg have demonstrated the use of elastic vibrations to manipulate the spin states of optically active color centers in SiC at room temperature. They show a non-trivial dependence of the acoustically induced spin transitions on the spin quantization direction, which can lead to chiral spin-acoustic resonances. These findings are important for applications in future quantum-electronic devices.
Approximately every two years the number of transistors on commercial chips has doubled - this phenomenon became known as "Moore's Law".But for several years now, Moore's law does not hold any more.Now, however, the next big miniaturization step could soon become possible - with so-called "two-dimensional (2D) materials" that may consist of only a single atomic layer.Research on semiconductor materials needed to fabricate transistors has seen significant progress in recent years.Today, ultra-thin semiconductors can be made of 2D materials, consisting of only a few atomic layers."There have already been transistor experiments with ultra-thin semiconductors, but until now they were coupled with ordinary insulators," says Tibor Grasser.
Weyl semimetals are a recently discovered class of materials, in which charge carriers behave the way electrons and positrons do in particle accelerators.Researchers from the Moscow Institute of Physics and Technology and Ioffe Institute in St. Petersburg have shown that these materials represent perfect gain media for lasers.The 21st-century physics is marked by the search for phenomena from the world of fundamental particles in tabletop materials.In some crystals, electrons move as high-energy particles in accelerators.MIPT physicists have turned this search inside-out, proving that reactions forbidden for elementary particles can also be forbidden in the crystalline materials known as Weyl semimetals.In a semiconductor laser, radiation results from the mutual annihilation of electrons and the positive charge carriers called holes.
It is based on the mutual destructive interference of two low-quality optical states in one resonator allowing for secure "trapping" of light in various materials even at small scales.The theoretical results of the work were confirmed experimentally, laying the basis for new miniature devices: effective sensors, optical filters and nonlinear light sources.The research paper is published in SPIE Advanced Photonics.In general, Fano resonances arise due to the interaction of two waves with a certain relation between the amplitudes and phases, for example, during the electromagnetic radiation scattering.The main parameters of Fano resonances, determining the peak width and asymmetry, were usually considered as independent.However, the scientists from ITMO University showed that the resonance parameters are connected: when the resonance peak in the spectrum of the scattered radiation becomes symmetric, its width becomes minimal, leading to the maximum Q factor.
Nanowires have the potential to revolutionize the technology around us.Measuring just 5-100 nanometers in diameter (a nanometer is a millionth of a millimeter), these tiny, needle-shaped crystalline structures can alter how electricity or light passes through them.They can emit, concentrate and absorb light and could therefore be used to add optical functionalities to electronic chips.They could, for example, make it possible to generate lasers directly on silicon chips and to integrate single-photon emitters for coding purposes.They could even be applied in solar panels to improve how sunlight is converted into electrical energy.But researchers from EPFL's Laboratory of Semiconductor Materials, run by Anna Fontcuberta i Morral, together with colleagues from MIT and the IOFFE Institute, have come up with a way of growing nanowire networks in a highly controlled and fully reproducible manner.
In collaboration with scientists from the Ioffe Institute, HSE University researchers have developed an ultra-sensitive atomic magnetometric scheme with a sensitivity of 5 fTl×Hz-1/2, setting a performance record for sensors operating in the Earth's magnetic field.The scheme will be used to design a multichannel atomic magnetoencephalograph, expected to be the most accurate and compact device available today for non-invasive measurement of the brain's electrical activity.The cost of the new atomic magnetoencephalograph is estimated to be five to seven times lower than that of existing devices, making it an affordable tool for diagnosing epilepsy and other neurodegenerative diseases in a broad population of patients.Several technologies are available today which allow physicians and researchers to detect and study brain activity non-invasively, without the need for surgery.Nevertheless, this is the most accurate and sensitive method of non-invasive functional brain mapping available today: under certain circumstances, it can differentiate millisecond scale bursts of activity in neural ensembles located a few millimetres apart.No more than 400 such systems are currently available worldwide, which significantly limits access to this technology essential for the detailed diagnosis of neurological diseases, for planning neurosurgical interventions, and for studying brain functioning and the direct and side effects of pharmachological interventions.
The international team of scientist of Peter the Great St. Petersburg Polytechnic University (SPbPU), Leibniz University Hannover (Leibniz Universität Hannover) and the Ioffe Institute found a way to improve nanocomposite material which opens a new opportunities to use it in hydrogen economy and other industries.The obtained results are explained in the academic article "The mechanism of charge carrier generation at the TiO2--n-Si heterojunction activated by gold nanoparticles" published in journal Semiconductor Science and Technology.In framework of the experiments the researchers of SPbPU, Leibniz University Hannover and Ioffe Institute propose a qualitative model to explain the complex processes.The scientific group used a composite material consisting of a silicon wafer (standard silicon wafer used in electronic devices), gold nanoparticles and a thin layer of titanium dioxide.It leads to the energy loss."The obtained material was a silicon wafer with pillar-like structures grown on its surface.
It turned out that abnormal graphene behavior can be fully characterised by Poisson ratio, which determines material capability to shrink or extend in transverse dimension.For instance, graphene shows extremely high mobility of electric charges, which can change drastically under elastic stress.Auxetics have a number of unusual features that will help improve existing technologies and create new ones.As the temperature rises, the conventional compound of such materials will tend to expand, but auxetic compound will compensate for this," comments Valentin Kachorovskii, a leading researcher at The Ioffe Institute and ITF.Authors of the new work managed to "reconcile" contradictory results of previous calculations and find parameters that exactly determine the Poisson ratio of graphene.Physicists found out that it is a variable value depending on tensile force applied.
Scientists designed the first subwavelength dielectric resonators for light trapping at the nanoscale that appears to be the simple silicon cylinder hundred times thinner than a human hair.Along with a simple shape and small size, it makes this new resonator a promising basis for a design of powerful nanolasers, biosensors, and various light transmitting devices.The results were published in Physical Review Letters.One of the most important tasks of the modern optics is to localize light inside a photonic system.Researchers from ITMO University, the Ioffe Institute and the Nonlinear Physics Center at the Australian National University have discovered a new way to improve the efficiency of optical resonators.This can be achieved by creating a structure where incoming light produces two waves of the same frequency yet different phases.