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Method for Measuring the Deviation from Lambert’s Cosine Law in the Diffuse Reflection of Ultracold Neutrons from Material Walls
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S0021364024603981
P. D. Grigoriev, V. D. Kochev, V. A. Tsyplukhin, A. M. Dyugaev, I. Ya. Polishchuk
{"title":"Method for Measuring the Deviation from Lambert’s Cosine Law in the Diffuse Reflection of Ultracold Neutrons from Material Walls","authors":"P. D. Grigoriev,&nbsp;V. D. Kochev,&nbsp;V. A. Tsyplukhin,&nbsp;A. M. Dyugaev,&nbsp;I. Ya. Polishchuk","doi":"10.1134/S0021364024603981","DOIUrl":"10.1134/S0021364024603981","url":null,"abstract":"<p>The simulation of the motion of ultracold neutrons is important for estimating their losses, accurately measuring their lifetimes, and describing other experiments. In material traps, it is necessary to take into account not only the specular reflection, but also the diffuse elastic reflection of ultracold neutrons from the walls of a trap. The angular distribution of diffusely reflected neutrons is usually described by Lambert’s cosine law, which does not have a strict theoretical justification and is often violated. In this work, an experiment has been proposed to measure the deviation of the angular distribution of diffusely reflected ultracold neutrons from Lambert’s cosine law. This deviation can be determined by the difference in the number of neutrons leaving a long, narrow trap for ultracold neutrons through its central and end windows. The performed Monte Carlo calculations corresponding to the proposed experiment have shown a significant effect for different shapes of the trap.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"873 - 878"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Superconducting Order Parameter of the RbCa2Fe4As4F2 Compound
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S0021364024604445
A. S. Usoltsev, A. T. Daniyarkhodzhaev, A. A. Gippius, A. V. Sadakov
{"title":"Superconducting Order Parameter of the RbCa2Fe4As4F2 Compound","authors":"A. S. Usoltsev,&nbsp;A. T. Daniyarkhodzhaev,&nbsp;A. A. Gippius,&nbsp;A. V. Sadakov","doi":"10.1134/S0021364024604445","DOIUrl":"10.1134/S0021364024604445","url":null,"abstract":"<p>The superconducting order parameter of the RbCa<sub>2</sub>Fe<sub>4</sub>As<sub>4</sub>F<sub>2</sub> compound belonging to the new 12442 family of iron-based superconductors with a critical temperature of <i>T</i><sub>c</sub> ~ 32 K has been studied. Two superconducting condensates with the order parameters Δ<sub>L</sub> ~ 6.3 meV and Δ<sub>S</sub> ~ 2.8 meV have been detected for the first time by multiple Andreev reflection spectroscopy. The temperature dependence of the superconducting critical current density <i>J</i><sub>c</sub>(<i>T</i>) in the intrinsic field has been measured. The approximation of the dependence <i>J</i><sub>c</sub>(<i>T</i>) demonstrates the correspondence of the experimental data to the double-gap model with the <i>s</i>-wave order parameter and the gaps of Δ<sub>L</sub> ~ 6 meV and Δ<sub>S</sub> ~ 2 meV. The superconducting order parameters obtained by two different methods are in good agreement with each other.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"923 - 931"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024604445.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Multilevel Relaxation Model for Describing Magnetization Curves of Nanoparticles
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S0021364024604196
A. V. Lobachev, M. A. Chuev
{"title":"Multilevel Relaxation Model for Describing Magnetization Curves of Nanoparticles","authors":"A. V. Lobachev,&nbsp;M. A. Chuev","doi":"10.1134/S0021364024604196","DOIUrl":"10.1134/S0021364024604196","url":null,"abstract":"<p>A theory has been developed to describe the magnetization curves of an ensemble of single-domain particles. This theory includes their temperature-induced excitations and is in fact a generalization of the two-level Stoner–Wohlfarth model and its relaxation version, as well as a multilevel relaxation model for describing Mössbauer spectra. A basically new aspect of this theory is the solution of a system of differential equations for nonequilibrium populations of stochastic states. The resultant model includes the physical mechanisms for the formation of magnetization curves of nanoparticles in real situations and describes self-consistently the qualitative features of the transformation of these curves under the variation of the temperature and the strength and direction of an external field.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"910 - 915"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024604196.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Control of Spin-Wave Bragg Resonances by the Spin Current in a Magnonic Crystal with Platinum Strips
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S002136402460455X
M. A. Morozova, O. V. Matveev, N. D. Lobanov, D. V. Romanenko, A. M. Mednikov, S. A. Gusev, N. S. Gusev, S. A. Nikitov
{"title":"Control of Spin-Wave Bragg Resonances by the Spin Current in a Magnonic Crystal with Platinum Strips","authors":"M. A. Morozova,&nbsp;O. V. Matveev,&nbsp;N. D. Lobanov,&nbsp;D. V. Romanenko,&nbsp;A. M. Mednikov,&nbsp;S. A. Gusev,&nbsp;N. S. Gusev,&nbsp;S. A. Nikitov","doi":"10.1134/S002136402460455X","DOIUrl":"10.1134/S002136402460455X","url":null,"abstract":"<p>The electric and magnetic frequency rearrangement of a Bragg resonance in the spectrum of spin waves in a magnonic crystal in the form of 100-nm-thick yttrium iron garnet film with attached 10-nm-thick platinum strips is reported. The effect of the spin current on the position of the Bragg band gap depends on the polarity of the voltage applied to the platinum strips. The positive voltage does not affect the band gap position, while the applied negative voltage lowers the band gap by about of 5 MHz. At frequencies outside the band gap, depending on the polarity of the voltage applied to platinum, either the enhancement or suppression of the spin wave is observed.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"916 - 922"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Numerical Simulation of a Photonic Tensor Core for the Hardware Acceleration of the Optical Matrix–Vector Multiplication
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S0021364024603956
G. A. Kolosov, A. S. Shorokhov, A. A. Fedyanin
{"title":"Numerical Simulation of a Photonic Tensor Core for the Hardware Acceleration of the Optical Matrix–Vector Multiplication","authors":"G. A. Kolosov,&nbsp;A. S. Shorokhov,&nbsp;A. A. Fedyanin","doi":"10.1134/S0021364024603956","DOIUrl":"10.1134/S0021364024603956","url":null,"abstract":"<p>A realistic numerical model of a photonic tensor core based on the crossbar architecture with absorbing GeSbTe chalcogenide glass films as weight elements of a photonic matrix has been developed. The performance of the model for the matrix–vector multiplication has been demonstrated. The possibility of using the tensor core based on the implemented architecture in convolutional neural networks for image recognition tasks has been shown. Numerical simulations have been used for the first time to estimate the potential performance and energy efficiency of a photonic hardware accelerator, taking into account the modern experimental element base.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"932 - 938"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024603956.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Two-Photon Ionization of Single Atoms Localized on the Bessel Beam Axis
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-02-14 DOI: 10.1134/S0021364024603762
M. D. Kiselev, E. V. Gryzlova, M. M. Popova, A. N. Grum-Grzhimailo
{"title":"Two-Photon Ionization of Single Atoms Localized on the Bessel Beam Axis","authors":"M. D. Kiselev,&nbsp;E. V. Gryzlova,&nbsp;M. M. Popova,&nbsp;A. N. Grum-Grzhimailo","doi":"10.1134/S0021364024603762","DOIUrl":"10.1134/S0021364024603762","url":null,"abstract":"<p>In the article the effect of twisting of Bessel radiation on two-photon ionization of single atoms localized on the axis of the incident beam is studied. The matrix element of two-photon ionization of this type is obtained for arbitrary polarization and multipolarity of the incident radiation. The differential and integral probability of ionization of an atom over the photoemission angle is analyzed. Illustrative calculations are performed for helium and neon atoms in the simplest case of a circularly polarized field in the electric dipole approximation in the single-active-electron model.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 12","pages":"879 - 885"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024603762.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Generalized Model of the Superconducting Sigma Neuron 超导Sigma神经元的广义模型
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-01-20 DOI: 10.1134/S0021364024603427
N. S. Shuravin, L. N. Karelina, A. S. Ionin, F. A. Razorenov, M. S. Sidel’nikov, S. V. Egorov, V. V. Bol’ginov
{"title":"Generalized Model of the Superconducting Sigma Neuron","authors":"N. S. Shuravin,&nbsp;L. N. Karelina,&nbsp;A. S. Ionin,&nbsp;F. A. Razorenov,&nbsp;M. S. Sidel’nikov,&nbsp;S. V. Egorov,&nbsp;V. V. Bol’ginov","doi":"10.1134/S0021364024603427","DOIUrl":"10.1134/S0021364024603427","url":null,"abstract":"<p>The superconducting sigma neuron is a single-junction interferometer, with a part of the circuit shunted by an additional inductance, which is also used to generate the output signal. It was previously predicted that the transfer function of this device would be close to the sigmoidal one at a certain relation between the values of inductance of its parts. This interferometer can be fabricated as a multilayer thin-film structure over a superconducting screen, which allows measuring the output magnetic flux in a single element. An analysis of the experimental data showed that the use of a superconducting screen did not ensure complete independence of the sigma neuron elements, as was assumed in the theoretical model. This paper presents a generalized model of the stationary state of a sigma neuron that takes into account the interaction between all its parts, including the input and readout elements.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 11","pages":"829 - 836"},"PeriodicalIF":1.4,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024603427.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Threshold Photogeneration of Biexcitons in Direct-Gap Semiconductor Nanocrystals 直接间隙半导体纳米晶体中双激子的阈值光产生
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-01-20 DOI: 10.1134/S0021364024603749
S. A. Fomichev, V. A. Burdov
{"title":"Threshold Photogeneration of Biexcitons in Direct-Gap Semiconductor Nanocrystals","authors":"S. A. Fomichev,&nbsp;V. A. Burdov","doi":"10.1134/S0021364024603749","DOIUrl":"10.1134/S0021364024603749","url":null,"abstract":"<p>The generation of two electron–hole pairs (a biexciton) in a nanocrystal of a direct-gap semiconductor with a nondegenerate conduction band upon the absorption of a single photon with the energy equal to twice the band gap of the nanocrystal is considered. It is shown that the process can take place only in the presence of the interaction of electrons both with each other and with the crystal-lattice field. The rate of this process is calculated and found to depend strongly on the nanocrystal size.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 11","pages":"822 - 828"},"PeriodicalIF":1.4,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Relaxation Phenomena in Dilute Charged Solutions 稀带电溶液中的弛豫现象
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-01-20 DOI: 10.1134/S0021364024604627
B. Timofeev, V. Shikin
{"title":"Relaxation Phenomena in Dilute Charged Solutions","authors":"B. Timofeev,&nbsp;V. Shikin","doi":"10.1134/S0021364024604627","DOIUrl":"10.1134/S0021364024604627","url":null,"abstract":"<p>The study of transport phenomena in conductive media of different dimensions often involves impedance diagnostics. The desire to exclude the influence of contact phenomena accompanying dc measurements on the current–voltage characteristic is a general reason for the application of complicated ac measurements instead of the quite methodologically simple dc regime. Relaxation phenomena in electrolytes with electrohydrodynamics linear in the density of the dopant <i>n</i><sub>d</sub> have been analyzed in detail in this work. It has been shown that the well-known Debye–Hückel–Onsager theory of the electrolyte conductivity cannot ensure the linearity of electrohydrodynamics of dilute solutions in the density <i>n</i><sub>d</sub>. Its linear alternative based on the theory of transport in finely dispersed two-phase systems called Maxwell formalism has been proposed. It has been shown that this allows one to interpret the observed relaxation time in the form <span>({{tau }_{c}} simeq RC)</span>, where <i>R</i> is the resistance of the bulk portion of a cell with an electrolyte in terms of the Maxwell formalism and <i>C</i> is the electrolytic capacitance of the metal–electrolyte transition regions appearing on its control electrodes. Examples of the successful use of <i>RC</i>-matched ac diagnostics have been discussed.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 11","pages":"843 - 853"},"PeriodicalIF":1.4,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Manifestation of Layer-by-Layer Localization of van Hove Singularities in Tunneling between Bilayer Graphene Sheets 双层石墨烯间隧道中范霍夫奇点逐层定位的表现
IF 1.4 4区 物理与天体物理
JETP Letters Pub Date : 2025-01-20 DOI: 10.1134/S0021364024604019
E. E. Vdovin, Yu. N. Khanin, S. V. Morozov, M. A. Kashchenko, A. A. Sokolik, K. S. Novoselov
{"title":"Manifestation of Layer-by-Layer Localization of van Hove Singularities in Tunneling between Bilayer Graphene Sheets","authors":"E. E. Vdovin,&nbsp;Yu. N. Khanin,&nbsp;S. V. Morozov,&nbsp;M. A. Kashchenko,&nbsp;A. A. Sokolik,&nbsp;K. S. Novoselov","doi":"10.1134/S0021364024604019","DOIUrl":"10.1134/S0021364024604019","url":null,"abstract":"<p>Tunneling between two sheets of bilayer graphene, the crystal lattices of which are rotated relative to each other by a small angle, has been studied. An anomalous behavior of the tunneling conductivity caused by van Hove singularities at the edges of the conduction and valence bands spatially localized in different sheets of bilayer graphene has been found.</p>","PeriodicalId":604,"journal":{"name":"JETP Letters","volume":"120 11","pages":"854 - 859"},"PeriodicalIF":1.4,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0021364024604019.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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