المؤلفون: Bodnar, Stanislav, Zerhoch, Jonathan, Liu, Shangpu, Shcherbakov, Andrii, Heindl, Markus W., Sapozhnik, Alexey, Deschler, Felix

مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Materials Science

الوصف: Using optical orientation to manipulate magnetic moments in matter with light is a key objective in opto-spintronics, however, realizations of such control on ultrafast timescales are limited. Here, we report ultrafast optical control of magnetic moment orientation in magnetically doped metal halide perovskites. Employing intense pulses of circularly polarized light, we inject populations of spin-polarized charge carriers in pristine and manganese-doped MAPbBr3 thin films. Using transient Faraday rotation spectroscopy, we probe the ultrafast magnetic moment dynamics following photoexcitation and find that light-induced magnetization in doped samples is increased by a factor of 10. We attribute this to photoexcited carriers acting on the magnetic moments of manganese dopant-ions via the sp-d exchange interaction, which forces them to align on picosecond timescales. Our findings open new avenues for device structures that use hybrid metal halide perovskites for ultrafast optical manipulation and read-out of magnetic order with the potential for high switching rates.

الوصول الحر: http://arxiv.org/abs/2406.19127Test

المؤلفون: Shcherbakov, Viktor, Krasnov, Fedor

المصدر: In Proceedings of the Seventh Workshop on e-Commerce and NLP, LREC-COLING 2024, pages 115-124, Torino, Italia. ELRA and ICCL

مصطلحات موضوعية: Computer Science - Information Retrieval, Computer Science - Computation and Language

الوصف: Product search is uniquely different from search for documents, Internet resources or vacancies, therefore it requires the development of specialized search systems. The present work describes the H1 embdedding model, designed for an offline term indexing of product descriptions at e-commerce platforms. The model is compared to other state-of-the-art (SoTA) embedding models within a framework of hybrid product search system that incorporates the advantages of lexical methods for product retrieval and semantic embedding-based methods. We propose an approach to building semantically rich term vocabularies for search indexes. Compared to other production semantic models, H1 paired with the proposed approach stands out due to its ability to process multi-word product terms as one token. As an example, for search queries "new balance shoes", "gloria jeans kids wear" brand entity will be represented as one token - "new balance", "gloria jeans". This results in an increased precision of the system without affecting the recall. The hybrid search system with proposed model scores mAP@12 = 56.1% and R@1k = 86.6% on the WANDS public dataset, beating other SoTA analogues.
Comment: 10 pages, 4 figures

الوصول الحر: http://arxiv.org/abs/2406.01233Test

المؤلفون: Utyushev, Anton D., Zakomirnyi, Vadim I., Shcherbakov, Alexey A., Rasskazov, Ilia L., Moroz, Alexander

مصطلحات موضوعية: Physics - Optics

الوصف: In an absorbing or an active host medium characterized by a complex refractive index $n_2=n_2'+{\rm i}n_2''$, our previously developed modified dipole long-wave approximation (MLWA) is shown to essentially overly with the exact Mie theory results for spherical nanoparticle with radius $a\lesssim 25$ nm ($a\lesssim 20$ nm) in the case of Ag and Au (Al and Mg) nanoparticles. The agreement for Au and Ag (Al and Mg) nanoparticles, slightly better in the case of Au than Ag, continues to be acceptable up to $a\sim 50$ nm ($a\sim 40$ nm), and can be used, at least qualitatively, up to $a\sim 70$~nm ($a\sim 50$ nm) correspondingly. A first order analytic perturbation theory (PT) in a normalized extinction coefficient, $\bar\kappa=n_2''/n_2'$, around a nonabsorbing host is developed within the dipole MLWA and its properties are investigated. It is shown that, in a suitable parameter range, the PT can reliably capture the effect of host absorption or gain on the extinction efficiency of various plasmonic nanoparticles.

الوصول الحر: http://arxiv.org/abs/2405.08903Test

المؤلفون: Sakib, Mashnoon Alam, Triplett, Brandon, Harris, William, Hussain, Naveed, Senichev, Alexander, Momenzadeh, Melika, Bocanegra, Joshua, Wu, Ruqian, Boltasseva, Alexandra, Shalaev, Vladimir M., Shcherbakov, Maxim R.

مصطلحات موضوعية: Physics - Optics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Quantum Physics

الوصف: Single photon emitters (SPEs) hosted in hexagonal boron nitride (hBN) are essential elementary building blocks for enabling future on-chip quantum photonic technologies that operate at room temperature. However, fundamental challenges, such as managing non-radiative decay, competing incoherent processes, as well as engineering difficulties in achieving deterministic placement and scaling of the emitters, limit their full potential. In this work, we experimentally demonstrate large-area arrays of plasmonic nanoresonators for Purcell-induced site-controlled SPEs by engineering emitter-cavity coupling and enhancing radiative emission at room temperature. The plasmonic nanoresonator architecture consists of gold-coated silicon pillars capped with an alumina spacer layer, enabling a 10-fold local field enhancement in the emission band of native hBN defects. Confocal photoluminescence and second-order autocorrelation measurements show bright SPEs with sub-30 meV bandwidth and a saturated emission rate of more than 3.8 million counts per second. We measure a Purcell factor of 4.9, enabling average SPE lifetimes of 480 ps, a five-fold reduction as compared to emission from gold-free devices, along with an overall SPE yield of 21%. Density functional theory calculations further reveal the beneficial role of an alumina spacer between defected hBN and gold, as an insulating layer can mitigate the electronic broadening of emission from defects proximal to gold. Our results offer arrays of bright, heterogeneously integrated quantum light sources, paving the way for robust and scalable quantum information systems.
Comment: 41 pages, 18 figures, supplementary information

الوصول الحر: http://arxiv.org/abs/2405.02516Test

المؤلفون: Ryabichev, Andrey, Shcherbakov, Konstantin

مصطلحات موضوعية: Mathematics - Combinatorics

الوصف: The main result of the article says that the formal power series equal to the ratio of two neighboring Chebyshev polynomials, after some renormalization, approximates the generating function of the Catalan numbers. We present a proof of this result using continued fractions. Also, for completeness of the presentation, we recall the basic properties of Chebyshev polynomials and formal power series that we use.
Comment: 8 pages, in Russian. Comments are welcome!

الوصول الحر: http://arxiv.org/abs/2403.04862Test

المؤلفون: Onodera, Tatsuhiro, Stein, Martin M., Ash, Benjamin A., Sohoni, Mandar M., Bosch, Melissa, Yanagimoto, Ryotatsu, Jankowski, Marc, McKenna, Timothy P., Wang, Tianyu, Shvets, Gennady, Shcherbakov, Maxim R., Wright, Logan G., McMahon, Peter L.

مصطلحات موضوعية: Physics - Optics, Computer Science - Emerging Technologies, Computer Science - Machine Learning

الوصف: On-chip photonic processors for neural networks have potential benefits in both speed and energy efficiency but have not yet reached the scale at which they can outperform electronic processors. The dominant paradigm for designing on-chip photonics is to make networks of relatively bulky discrete components connected by one-dimensional waveguides. A far more compact alternative is to avoid explicitly defining any components and instead sculpt the continuous substrate of the photonic processor to directly perform the computation using waves freely propagating in two dimensions. We propose and demonstrate a device whose refractive index as a function of space, $n(x,z)$, can be rapidly reprogrammed, allowing arbitrary control over the wave propagation in the device. Our device, a 2D-programmable waveguide, combines photoconductive gain with the electro-optic effect to achieve massively parallel modulation of the refractive index of a slab waveguide, with an index modulation depth of $10^{-3}$ and approximately $10^4$ programmable degrees of freedom. We used a prototype device with a functional area of $12\,\text{mm}^2$ to perform neural-network inference with up to 49-dimensional input vectors in a single pass, achieving 96% accuracy on vowel classification and 86% accuracy on $7 \times 7$-pixel MNIST handwritten-digit classification. This is a scale beyond that of previous photonic chips relying on discrete components, illustrating the benefit of the continuous-waves paradigm. In principle, with large enough chip area, the reprogrammability of the device's refractive index distribution enables the reconfigurable realization of any passive, linear photonic circuit or device. This promises the development of more compact and versatile photonic systems for a wide range of applications, including optical processing, smart sensing, spectroscopy, and optical communications.

الوصول الحر: http://arxiv.org/abs/2402.17750Test

المؤلفون: Ryabichev, Andrey, Shcherbakov, Konstantin

مصطلحات موضوعية: Mathematics - Classical Analysis and ODEs

الوصف: Given a real cubic function $f(x)$ with three roots, take an equilateral triangle $ABC$, the projections of which vertices are the roots of $f(x)$. There is a folklore fact that the vertical lines through the extrema of $f(x)$ are tangent to the inscribed circle of $ABC$. We generalise this fact to a regular $n$-gon and the corresponding degree $n$ polynomial.
Comment: 7 pages, in Russian, 3 figures. Comments are welcome!

الوصول الحر: http://arxiv.org/abs/2401.12394Test

المؤلفون: da Costa, Conrado, Menshikov, Mikhail, Shcherbakov, Vadim, Wade, Andrew

المصدر: Stochastic Processes and their Applications, Vol. 176 (2024), article 104420

مصطلحات موضوعية: Mathematics - Probability, 60J10 (Primary) 60G50, 60K50, 60F05, 60F15 (Secondary)

الوصف: We quantify superdiffusive transience for a two-dimensional random walk in which the vertical coordinate is a martingale and the horizontal coordinate has a positive drift that is a polynomial function of the individual coordinates and of the present time. We describe how the model was motivated through an heuristic connection to a self-interacting, planar random walk which interacts with its own centre of mass via an excluded-volume mechanism, and is conjectured to be superdiffusive with a scale exponent $3/4$. The self-interacting process originated in discussions with Francis Comets.
Comment: 26 pages, 4 figures; v2: minor revision

الوصول الحر: http://arxiv.org/abs/2401.07813Test

المؤلفون: Shcherbakov, Vadim

المصدر: Markov Processes and Related Fields, 2023, volume 29, Issue 4

مصطلحات موضوعية: Mathematics - Probability, Mathematical Physics

الوصف: This survey concerns probabilistic models motivated by cooperative sequential adsorption (CSA) models. CSA models are widely used in physics and chemistry for modelling adsorption processes in which adsorption rates depend on the spatial configuration of already adsorbed particles. Corresponding probabilistic models describe random sequential allocation of particles either in a subset of Euclidean space, or at vertices of a graph. Depending on a technical setup these probabilistic models are stated in terms of spatial or integer-valued interacting birth-and-death processes. In this survey we consider several such models that have been studied in recent years.

الوصول الحر: http://arxiv.org/abs/2312.13731Test

المؤلفون: Shcherbakov, Dmitry, Voigt, Greyson, Memaran, Shahriar, Liu, Gui-Bin, Wang, Qiyue, Watanabe, Kenji, Taniguchi, Takashi, Smirnov, Dmitry, Balicas, Luis, Zhang, Fan, Lau, Chun Ning

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: A two-dimensional (2D) quantum electron system is characterized by the quantized energy levels, or subbands, in the out-of-plane direction. Populating higher subbands and controlling the inter-subband transitions have wide technological applications such as optical modulators and quantum cascade lasers. In conventional materials, however, the tunability of intersubband spacing is limited. Here we demonstrate electrostatic population and characterization of the second subband in few-layer InSe quantum wells, with giant tunability of its energy, population, and spin-orbit coupling strength, via the control of not only layer thickness but also out-of-plane displacement field. A modulation of as much as 350% or over 250 meV is achievable, underscoring the promise of InSe for tunable infrared and THz sources, detectors and modulators.

الوصول الحر: http://arxiv.org/abs/2312.03228Test