Articles de revues : « Brillouin memory »

1

Chen, Yao, Fangxing Zhang, Tian Qin, Guolin Zhao, Jiankun Hou, Xianfeng Chen, Li Ge et Wenjie Wan. « Exceptional points with memory in a microcavity Brillouin laser ». Optica 9, n^o 9 (23 août 2022) : 971. http://dx.doi.org/10.1364/optica.456977.

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Exceptional points (EPs), universally present in non-Hermitian systems, often reveal some critical behaviors such as topological encircling chirality and ultrahigh enhanced sensing near such singularities. However, most of the experimental realizations of EPs have been limited to the linear regime, where system nonlinearity has been omitted. Here, we experimentally observe two distinct EPs with opposite hermiticities and demonstrate a parity–time phase transition with exotic memory effects near the EPs in a nonlinear and non-Hermitian system based on a stimulated Brillouin laser in an optical microcavity. The self-phase modulation induced nonlinearity effectively alters the EP location, surprisingly, in an asymmetric manner, resulting in a bistable memory effect. Moreover, two EPs with opposite hermiticities in the same system are found to show quite distinct behaviors in such a memory effect. This scheme completes the studies of non-Hermitian physics in a more general scenario by including nonlinearity and paves the way toward optical memory for all-optical signal processing and quantum information.

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Zerbib, Maxime, Maxime Romanet, Thibaut Sylvestre, Christian Wolff, Birgit Stiller, Jean-Charles Beugnot et Kien Phan Huy. « Spin-orbit interaction through Brillouin scattering in nanofibers ». EPJ Web of Conferences 287 (2023) : 06011. http://dx.doi.org/10.1051/epjconf/202328706011.

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Spin-orbit interactions (SOI), describing the transfer of a spin degree of freedom to an orbital angular momentum (OAM), have been widely explored in recent opto-acoustic studies for applications mainly in spintronics and for topological insulators [1]. We report the observation of SOI by Brillouin scattering in an optical nanofiber. Specifically, we describe the transfer of a spin degree of freedom from light incident to the nanofiber to an acoustic vortex with a topological charge of order 2 in the form of OAM. Coupled with the phase matching condition for the energy conservation during Brillouin scattering, it results in a backscattered wave with a spin opposite to the incident wave. This observation allows considering applications of opto-acoustic Brillouin memory based on polarization conversion through a SOI [2].

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Steelman, Zachary A., Andrew C. Weems, Andrew J. Traverso, Jason M. Szafron, Duncan J. Maitland et Vladislav V. Yakovlev. « Revealing the glass transition in shape memory polymers using Brillouin spectroscopy ». Applied Physics Letters 111, n^o 24 (11 décembre 2017) : 241904. http://dx.doi.org/10.1063/1.4999803.

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4

Dürr, Stephan. « Optimization of the Brillouin operator on the KNL architecture ». EPJ Web of Conferences 175 (2018) : 02001. http://dx.doi.org/10.1051/epjconf/201817502001.

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Experiences with optimizing the matrix-times-vector application of the Brillouin operator on the Intel KNL processor are reported. Without adjustments to the memory layout, performance figures of 360 Gflop/s in single and 270 Gflop/s in double precision are observed. This is with Nc = 3 colors, Nv = 12 right-hand-sides, Nthr = 256 threads, on lattices of size 323 × 64, using exclusively OMP pragmas. Interestingly, the same routine performs quite well on Intel Core i7 architectures, too. Some observations on the much harderWilson fermion matrix-times-vector optimization problem are added.

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Riley, Grant A., Justin M. Shaw, Thomas J. Silva et Hans T. Nembach. « Simultaneous measurement of the exchange parameter and saturation magnetization using propagating spin waves ». Applied Physics Letters 120, n^o 11 (14 mars 2022) : 112405. http://dx.doi.org/10.1063/5.0083583.

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The exchange interaction in ferromagnetic ultra thin films is a critical parameter in magnetization-based storage and logic devices, yet the accurate measurement of it remains a challenge. While a variety of approaches are currently used to determine the exchange parameter, each has its limitations, and good agreement among them has not been achieved. To date, neutron scattering, magnetometry, Brillouin light scattering, spin-torque ferromagnetic resonance spectroscopy, and Kerr microscopy have all been used to determine the exchange parameter. Here, we present a method that exploits the wavevector selectivity of Brillouin light scattering to measure the spin wave dispersion in both the backward volume and Damon–Eshbach orientations. The exchange, saturation magnetization, and magnetic thickness are then determined by a simultaneous fit of both dispersion branches with general spin wave theory without any prior knowledge of the thickness of a magnetic “dead layer.” In this work, we demonstrate the strength of this technique for ultrathin metallic films, typical of those commonly used in industrial applications for magnetic random-access memory.

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Khusnutdinoff, R. M. « Dynamics of Liquid Lithium Atoms : Time Scales and Dynamic Correlation Functions ». Nonlinear Phenomena in Complex Systems 23, n^o 1 (14 avril 2020) : 90–96. http://dx.doi.org/10.33581/1561-4085-2020-23-1-90-96.

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Based on the configuration data on molecular dynamics simulation of the lithium melt near the melting point, the memory functions of the relaxation process of the density fluctuations are calculated. It is established that for the range of wave numbers corresponding to microscopic spatial scales, the memory functions of the first four orders are characterized by oscillating behavior. This feature indicates that the model memory functions in the case of phenomenological description of the dynamics of the density fluctuations can not have the form of monotonically decreasing functions. The frequency characteristics of the dynamic structure factor for a wide range of wave numbers are calculated. The convergence of the relaxation parameters Δ4(k) and Δ5(k) for the range of wave numbers from the hydrodynamic regime (k → 0) to the values of k is higher than the boundary of the first pseudo-Brillouin zone (for k ≈ 0.87km) are detected. The characteristic time scales of the process of structural relaxation of the density fluctuations are determined.

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SHANG Qiufeng, 尚秋峰, et 李雪丽 LI Xueli. « 基于LSTM的布里渊增益谱提取方法 ». ACTA PHOTONICA SINICA 52, n^o 1 (2023) : 0106004. http://dx.doi.org/10.3788/gzxb20235201.0106004.

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Kotlicki, Omer, et Jacob Scheuer. « Thermal self-stability, multi-stability, and memory effects in single-mode Brillouin fiber lasers ». Optics Express 25, n^o 22 (23 octobre 2017) : 27321. http://dx.doi.org/10.1364/oe.25.027321.

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Matveyev, A. Z., et G. A. Pasmanik. « Realization of associative memory with the aid of a nonlinear selective stimulated-Brillouin-scattering mirror ». Quantum Electronics 23, n^o 5 (31 mai 1993) : 426–31. http://dx.doi.org/10.1070/qe1993v023n05abeh003088.

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Melin, Jeanette, Stefan Cano et Leslie Pendrill. « The Role of Entropy in Construct Specification Equations (CSE) to Improve the Validity of Memory Tests ». Entropy 23, n^o 2 (9 février 2021) : 212. http://dx.doi.org/10.3390/e23020212.

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Commonly used rating scales and tests have been found lacking reliability and validity, for example in neurodegenerative diseases studies, owing to not making recourse to the inherent ordinality of human responses, nor acknowledging the separability of person ability and item difficulty parameters according to the well-known Rasch model. Here, we adopt an information theory approach, particularly extending deployment of the classic Brillouin entropy expression when explaining the difficulty of recalling non-verbal sequences in memory tests (i.e., Corsi Block Test and Digit Span Test): a more ordered task, of less entropy, will generally be easier to perform. Construct specification equations (CSEs) as a part of a methodological development, with entropy-based variables dominating, are found experimentally to explain (r=R2 = 0.98) and predict the construct of task difficulty for short-term memory tests using data from the NeuroMET (n = 88) and Gothenburg MCI (n = 257) studies. We propose entropy-based equivalence criteria, whereby different tasks (in the form of items) from different tests can be combined, enabling new memory tests to be formed by choosing a bespoke selection of items, leading to more efficient testing, improved reliability (reduced uncertainties) and validity. This provides opportunities for more practical and accurate measurement in clinical practice, research and trials.

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Graczykowski, B., S. Mielcarek, T. Breczewski, M. L. No, J. San-Juan et B. Mroz. « Martensitic phase transition in Cu–14%Al–4%Ni shape memory alloys studied by Brillouin light scattering ». Smart Materials and Structures 22, n^o 8 (16 juillet 2013) : 085027. http://dx.doi.org/10.1088/0964-1726/22/8/085027.

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Graczykowski, B., B. Mroz, S. Mielcarek, T. Breczewski, M. L. Nó et J. San Juan. « Surface acoustic waves and elastic constants of Cu14%Al4%Ni shape memory alloys studied by Brillouin light scattering ». Journal of Physics D : Applied Physics 44, n^o 45 (28 octobre 2011) : 455307. http://dx.doi.org/10.1088/0022-3727/44/45/455307.

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Melin, Jeanette, Stefan Cano, Agnes Flöel, Laura Göschel et Leslie Pendrill. « The Role of Entropy in Construct Specification Equations (CSE) to Improve the Validity of Memory Tests : Extension to Word Lists ». Entropy 24, n^o 7 (5 juillet 2022) : 934. http://dx.doi.org/10.3390/e24070934.

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Metrological methods for word learning list tests can be developed with an information theoretical approach extending earlier simple syntax studies. A classic Brillouin entropy expression is applied to the analysis of the Rey’s Auditory Verbal Learning Test RAVLT (immediate recall), where more ordered tasks—with less entropy—are easier to perform. The findings from three case studies are described, including 225 assessments of the NeuroMET2 cohort of persons spanning a cognitive spectrum from healthy older adults to patients with dementia. In the first study, ordinality in the raw scores is compensated for, and item and person attributes are separated with the Rasch model. In the second, the RAVLT IR task difficulty, including serial position effects (SPE), particularly Primacy and Recency, is adequately explained (Pearson’s correlation R=0.80) with construct specification equations (CSE). The third study suggests multidimensionality is introduced by SPE, as revealed through goodness-of-fit statistics of the Rasch analyses. Loading factors common to two kinds of principal component analyses (PCA) for CSE formulation and goodness-of-fit logistic regressions are identified. More consistent ways of defining and analysing memory task difficulties, including SPE, can maintain the unique metrological properties of the Rasch model and improve the estimates and understanding of a person’s memory abilities on the path towards better-targeted and more fit-for-purpose diagnostics.

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Chan, Chun-Wen, Chia-Yun Hsieh, Fang-Mei Chan, Pin-Jia Huang et Chao-Yao Yang. « Valley Spin–Polarization of MoS2 Monolayer Induced by Ferromagnetic Order in an Antiferromagnet ». Materials 17, n^o 16 (8 août 2024) : 3933. http://dx.doi.org/10.3390/ma17163933.

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Transition metal dichalcogenide (TMD) monolayers exhibit unique valleytronics properties due to the dependency of the coupled valley and spin state at the hexagonal corner of the first Brillouin zone. Precisely controlling valley spin-polarization via manipulating the electron population enables its application in valley-based memory or quantum technologies. This study uncovered the uncompensated spins of the antiferromagnetic nickel oxide (NiO) serving as the ferromagnetic (FM) order to induce valley spin-polarization in molybdenum disulfide (MoS2) monolayers via the magnetic proximity effect (MPE). Spin-resolved photoluminescence spectroscopy (SR-PL) was employed to observe MoS2, where the spin-polarized trions appear to be responsible for the MPE, leading to a valley magnetism. Results indicate that local FM order from the uncompensated surface of NiO could successfully induce significant valley spin-polarization in MoS2 with the depolarization temperature approximately at 100 K, which is relatively high compared to the related literature. This study reveals new perspectives in that the precise control over the surface orientation of AFMs serves as a crystallographic switch to activate the MPE and the magnetic sustainability of the trion state is responsible for the observed valley spin-polarization with the increasing temperature, which promotes the potential of AFM materials in the field of exchange-coupled Van der Waals heterostructures.

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Stiller, Birgit, Kevin Jaksch, Johannes Piotrowski, Moritz Merklein, Mikołaj K. Schmidt, Khu Vu, Pan Ma et al. « Brillouin light storage for 100 pulse widths ». npj Nanophotonics 1, n^o 1 (2 mai 2024). http://dx.doi.org/10.1038/s44310-024-00004-x.

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AbstractSignal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150 ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses, and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realization of practical Brillouin-based delay lines and other optical processing applications.

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Chen, Wenhui. « On the Cauchy problem for acoustic waves in hereditary fluids : Decay properties and inviscid limits ». Mathematical Methods in the Applied Sciences, 27 mai 2024. http://dx.doi.org/10.1002/mma.10242.

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This paper considers the viscous/inviscid Moore–Gibson–Thompson (MGT) equations with memory of type I in the whole space . For one thing, associating with a new condition on initial data, we derive the optimal estimates and the optimal leading term of the acoustic velocity potential for large time, where we analyze different contributions from viscous, thermally relaxing, as well as hereditary fluids on large time asymptotic behavior for the acoustic waves models. For another, by using the multiscale analysis and energy methods in the Fourier space, we demonstrate the inviscid limits (i.e., as the diffusivity of sound tends to zero), which match our Wentzel‐Kramers‐Brillouin (WKB) expansion of the solution. Finally, we give a further application of our results on large time behavior for the nonlinear Jordan‐MGT equation in viscous hereditary fluids.

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Seo, Dongpyo, S. Hwang, Byungro Kim, Yeonhee Yang, Seungha Yoon et B. K. Cho. « Tunable asymmetric spin wave excitation and propagation in a magnetic system with two rectangular blocks ». Scientific Reports 11, n^o 1 (décembre 2021). http://dx.doi.org/10.1038/s41598-021-02967-9.

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AbstractAsymmetric spin wave excitation and propagation are key properties to develop spin-based electronics, such as magnetic memory, spin information and logic devices. To date, such nonreciprocal effects cannot be manipulated in a system because of the geometrical magnetic configuration, while large values of asymmetry ratio are achieved. In this study, we suggest a new magnetic system with two blocks, in which the asymmetric intensity ratio can be changed between 0.276 and 1.43 by adjusting the excitation frequency between 7.8 GHz and 9.4 GHz. Because the two blocks have different widths, they have their own spin wave excitation frequency ranges. Indeed, the spin wave intensities in the two blocks, detected by the Brillouin light scattering spectrum, were observed to be frequency-dependent, yielding tuneable asymmetry ratio. Thus, this study provides a new path to enhance the application of spin waves in spin-based electronics.

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Vila, Marc. « Giant Resistance Switch in Twisted Transition Metal Dichalcogenide Tunnel Junctions ». 2D Materials, 30 juillet 2024. http://dx.doi.org/10.1088/2053-1583/ad690f.

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Abstract Resistance switching in multilayer structures are typically based on materials possessing ferroic orders. Here we predict an extremely large resistance switching based on the relative spin-orbit splitting in twisted transition metal dichalcogenide (TMD) monolayers tunnel junctions. Because of the valence band spin splitting which depends on the valley index in the Brillouin zone, the perpendicular electronic transport through the junction depends on the relative reciprocal space overlap of the spin-dependent Fermi surfaces of both layers, which can be tuned by twisting one layer. Our quantum transport calculations reveal a switching resistance larger than 106% when the relative alignment of TMDs goes from 0º to 60º and when the angle is kept ﬁxed at 60º and the Fermi level is varied. By creating vacancies, we evaluate how inter-valley scattering aﬀects the eﬃciency and ﬁnd that the resistance switching remains large (104%) for typical values of vacancy concentration. Not only should this resistance switching be observed at room temperature due to the large spin splitting, but our results also show how twist angle engineering and control of van der Waals heterostructures could be used for next-generation memory and electronic applications.

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Dubey, Digvijay Nath, Gurvinderjit Singh, Akhilesh Kumar Singh et Saurabh Tripathi. « Role of Γ4- phonon mode in the enhancement of ferroelectric polarization in a perovskite-based eco-friendly functional material ». Europhysics Letters, 7 octobre 2022. http://dx.doi.org/10.1209/0295-5075/ac985d.

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Abstract We report here the role of component freezing of three dimensional polar (Γ4-) phonon mode corresponding to the center of cubic Brillouin zone in tuning the structure-property correlations of a scientifically enriched and technologically important barium titanate based eco-friendly functional material (Ba0.92Ca0.08)(Zr0.05Ti0.95-xSnx)O3; BCZTSnx (0 ≤ x ≤ 0.10) synthesized via solid-state reaction method. The combined X-ray diffraction, Raman spectroscopic analysis, and temperature-dependent dielectric studies have revealed the presence of several crystallographic phase transitions with coexisting phases viz., P4mm→(P4mm + Amm2 + R3m)→(Amm2 + R3m)→R3m→(Pm3m+R3m), as a function of Sn(x) content. These crystallographic phases viz; P4mm, Amm2, and R3m results due to freezing of the component(s) of Γ4- phonon mode (belonging to Pm3m space group), with the respective order parameter directions (0,0,a), (a,a,0), and (a,a,a) leading to ferroelectric polarization along ⟨001⟩, ⟨110⟩ and ⟨111⟩ directions, respectively. The ceramic composition corresponding to x=0.025 exhibits a significant reduction in the coercive field (Ec) and an enhancement in ferroelectric polarization (Pr) in comparison to x=0, inferred from PE loop measurements. The enhancement in ferroelectric polarization at x=0.025 has been attributed to the inter-ferroelectric threephase (P4mm + Amm2 + R3m) coexistence around this composition, and significantly enhanced amplitudes of ferroelectric phonon modes corresponding to orthorhombic and rhombohedral phases, calculated using the symmetry mode analysis technique. The existence of a high ferroelectric polarization and low coercive field may lead to x=0.025 composition as an eco-friendly candidate for ferroelectric memory devices.

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Sharan, Abhishek, Stephan Lany et Nirpendra Singh. « Computational Discovery of Two-Dimensional Rare-Earth Iodides : Promising Ferrovalley Materials for Valleytronics ». 2D Materials, 14 décembre 2022. http://dx.doi.org/10.1088/2053-1583/acab72.

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Abstract Two-dimensional Ferrovalley materials with intrinsic valley polarization are rare but highly promising for valley-based nonvolatile random access memory and valley filter. Using Kinetically Limited Minimization (KLM), an unconstrained crystal structure prediction algorithm, and prototype sampling based on first-principles calculations, we have discovered 17 new Ferrovalley materials (rare-earth iodides RI2, where R is a rare-earth element belonging to Sc, Y, or La-Lu, and I is Iodine). The rare-earth iodides are layered and demonstrate 2H, 1T, or 1Td phase as the ground-state in bulk, analogous to transition metal dichalcogenides (TMDCs). The calculated exfoliation energy of monolayers is comparable to that of graphene and TMDCs, suggesting possible experimental synthesis. The monolayers in the 2H phase exhibit two-dimensional ferromagnetism due to unpaired electrons in d and f orbitals. Throughout the rare-earth series, d bands show valley polarization at K and K' points in the Brillouin zone near the Fermi level. Due to strong magnetic exchange interaction and spin-orbit coupling, large intrinsic valley polarization in the range of 15-143 meV without external stimuli is observed, which can be tuned and enhanced by applying a biaxial strain. These valleys can selectively be probed and manipulated for information storage and processing, potentially offering superior performance beyond conventional electronics and spintronics. We further show that the 2H ferromagnetic phase of RI2 monolayers possesses non-zero Berry curvature and exhibits the valley Hall effect with considerable anomalous Hall conductivity. Our work will incite exploratory synthesis of the predicted Ferrovalley materials and their application in valleytronics and beyond.

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Articles de revues sur le sujet « Brillouin memory »

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