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Strain control of layer-resolved negative capacitance in superlattices

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npj Computational Materials 2020年第1期6卷 127-130页

作者： Raymond Walter Sergey Prosandeev Charles Paillard l.bellaiche Department of Physics and Institute for Nanoscience and Engineering University of ArkansasFayettevilleAR 72701USA Department of Mathematical Sciences University of ArkansasFayettevilleAR 72701USA Identity Engineering Kinesso LLCConwayAR 72032USA Institute of Physics and Physics Department of Southern Federal University Rostov-na-Donu 344090Russia laboratoire Structures Propriétés et Modélisation des SolidesCentraleSupélecUMR CNRS 8580UniversitéParis-Saclay91190 Gif-sur-YvetteFrance

Negative capacitance in BaTiO_(3)/SrTiO_(3) superlattices is investigated by Monte Carlo simulations in an atomistic effective Hamiltonian model,using fluctuation formulas for responses to the local macroscopic field that incorporates depolarizing *** show that epitaxial strain can tune the negative capacitance of the BaTiO_(3) ferroelectric layer and the overall capacitance of the *** addition,we predict and explain an original switching of the negative capacitance from the BaTiO3 layer to the SrTiO_(3) layer at low temperatures for intermediate strains.

关键词： capacitance layer resolved

An ensemble deep learning based IDS for IoT using lambda architecture

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Cybersecurity 2023年第3期6卷 1-17页

作者： Rubayyi Alghamdi Martine bellaiche Computer and Software Engineering Department école PolytechniqueMontrealCanada

The Internet of Things(IoT)has revolutionized our world today by providing greater levels of accessibility,connectivity and ease to our everyday *** enables massive amounts of data to be traversed across multiple heterogeneous devices that are all *** phenomenon makes IoT networks vulnerable to various network attacks and *** an Intrusion Detection System(IDS)for IoT networks is challenging as they enable a massive amount of data to be aggregated,which is difficult to handle and analyze in real time mainly because of the heterogeneous nature of IoT *** inefficient,traditional IDS approach accentuates the need to develop advanced IDS techniques by employing Machine or Deep *** paper presents a deep ensemble-based IDS using lambda architecture by following a multi-pronged classification *** classification uses long Short Term Memory(lSTM)to differentiate between malicious and benign traffic,while the multi-class classifier uses an ensemble of lSTM,Convolutional Neural Network and Artificial Neural Network classifiers to detect the type of *** model training is performed in the batch layer,while real-time evaluation is carried out through model inferences in the speed layer of the lambda *** proposed approach gives high accuracy of over 99.93%and saves useful processing time due to the multi-pronged classification strategy and using the lambda architecture.

关键词： IoT IDS lambda architecture Cyber-attacks Deep learning Ensemble learning

Ferroelectricity in Charge-Ordering Crystals with Centrosymmetric lattices

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Chinese Physics letters 2022年第9期39卷 76-80页

作者： Yali Yang laurent bellaiche Hongjun Xiang Key laboratory of Computational Physical Sciences(Ministry of Education) State Key Laboratory of Surface Physicsand Department of PhysicsFudan UniversityShanghai 200433China Shanghai Qizhi Institution Shanghai 200232China Physics Department and Institute for Nanoscience and Engineering University of ArkansasFayettevilleArkansas 72701USA

The switchability between the two ferroelectric(FE)states of an FE material makes FEs widely used in memories and other electronic ***,for conventional FEs,its FE switching only occurs between the two FE states whose spatial inversion symmetry is *** search for FE materials is therefore subject to certain *** propose a new type of FEs whose FE states still contain spatial inversion *** change in polarization of this new type of FEs originates from electronic transfer between two centrosymmetric FE states under an external electric *** BaBiO_(3) as an example,we show that charge-ordering systems can be a typical representative of this new type of ***,unlike traditional ferroelectrics,the change in polarization in this new type of FEs is quantum in nature with the direction dependent on the specific FE transition *** work therefore not only extends the concept of FEs but may also open up a new way to find multiferroics.

关键词： polarization lattice symmetric

Dynamics of antipolar distortions

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npj Computational Materials 2017年第1期3卷 171-178页

作者： Kinnary Patel Sergey Prosandeev laurent bellaiche Physics Department and Institute for Nanoscience and Engineering University of ArkansasFayettevilleAR 72701USA Institute of Physics and Physics Department of Southern Federal University Rostov-na-Donu 344090Russia

Materials possessing antipolar cation motions are currently receiving a lot of attention because they are fundamentally intriguing while being technologically *** studies devoted to these complex materials have focused on their static properties or on their zone-center *** a result,some important dynamics of antipolar cation distortions,such as the temperature behavior of their phonon frequencies,have been much less investigated,despite the possibility to exhibit unusual ***,we report the results and analysis of atomistic simulations revealing and explaining such dynamics for BiFeO3 bulks being subject to hydrostatic *** is first predicted that cooling such material yields the following phase transition sequence:the cubic paraelectric Pm3m state at high temperature,followed by an intermediate phase possessing long-range-ordered in-phase oxygen octahedral tiltings,and then the Pnma state that is known to possess antipolar cation motions in addition to in-phase and antiphase oxygen octahedral *** cation modes are found to all have high phonon frequencies that are independent of temperature in the paraelectric *** the other hand and in addition to antipolar cation modes increasing in number,some phonons possessing antipolar cation character are rather soft in the intermediate and Pnma *** of our data combined with the development of a simple model reveals that such features originate from a dynamical mixing between pure antipolar cation phonons and fluctuations of oxygen octahedral tiltings,as a result of a specific trilinear energetic *** developed model can also be easily applied to predict dynamics of antipolar cation motions for other possible structural paths bringing Pm3m to Pnma states.

关键词： polar distortion phonon

Strain engineering of electro-optic constants in ferroelectric materials

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npj Computational Materials 2019年第1期5卷 1092-1096页

作者： Charles Paillard Sergei Prokhorenko laurent bellaiche Department of Physics and Institute for Nanoscience and Engineering University of ArkansasFayettevilleAR 72701USA

Electro-optic effects allow control of the ow of light using electric fields,and are of utmost importance for today’s information and communication technologies,such as TV displays and fiber *** search for large electro-optic constants in films is essential to the miniaturization and increased efficiency of electro-optic *** this work,we demonstrate that strain-engineering in PbTiO_(3) films allows to selectively choose which electro-optic constant to *** electro-optic constants larger than 100 pm V^(−1) are predicted,either by driving the softening of an optical phonon mode at a phase transition boundary under tensile strain,or by generating the equivalent of a negative pressure via compressive strain to obtain large piezoelectric *** particular,a r_(13) electro-optic coefficient twice as large as the one of the commonly used liNbO_(3) electro-optic material is found here when growing PbTiO_(3) on the technologicallyimportant Si substrate.

关键词： softening constants ferroelectric

Interplay between Kitaev interaction and single ion anisotropy in ferromagnetic CrI_(3) and CrGeTe_(3) monolayers

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npj Computational Materials 2018年第1期4卷 185-190页

作者： Changsong Xu Junsheng Feng Hongjun Xiang laurent bellaiche Physics Department and Institute for Nanoscience and Engineering University of ArkansasFayettevilleAR 72701USA Key laboratory of Computational Physical Sciences(Ministry of Education) State Key Laboratory of Surface Physicsand Department of PhysicsFudan University200433 ShanghaiChina School of Physics and Materials Engineering Hefei Normal University230601 HefeiChina Collaborative Innovation Center of Advanced Microstructures 210093 NanjingChina

Magnetic anisotropy is crucially important for the stabilization of two-dimensional(2D)magnetism,which is rare in nature but highly desirable in spintronics and for advancing fundamental *** works on CrI3 and CrGeTe_(3) monolayers not only led to observations of the long-time-sought 2D ferromagnetism,but also revealed distinct magnetic anisotropy in the two systems,namely Ising behavior for CrI3 versus Heisenberg behavior for CrGeTe_(3).Such magnetic difference strongly contrasts with structural and electronic similarities of these two materials,and understanding it at a microscopic scale should be of large ***,firstprinciples calculations are performed and analyzed to develop a simple Hamiltonian,to investigate magnetic anisotropy of CrI3 and CrGeTe_(3) *** anisotropic exchange coupling in both systems is surprisingly determined to be of ***,the interplay between this Kitaev interaction and single ion anisotropy(SIA)is found to naturally explain the different magnetic behaviors of CrI3 and CrGeTe_(3).Finally,both the Kitaev interaction and SIA are further found to be induced by spin–orbit coupling of the heavy ligands(I of CrI3 or Te of CrGeTe_(3))rather than the commonly believed 3d magnetic Cr ions.

关键词： anisotropy interaction coupling

large scale hybrid Monte Carlo simulations for structure and property prediction

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npj Computational Materials 2018年第1期4卷 1-7页

作者： Sergei Prokhorenko Kruz Kalke Yousra Nahas laurent bellaiche Physics Department and Institute for Nanoscience and Engineering University of ArkansasFayettevilleAR 72701USA

The Monte Carlo method is one of the first and most widely used algorithms in modern computational *** condensed matter physics,the particularly popular flavor of this technique is the Metropolis Monte Carlo *** being incredibly robust and easy to implement,the Metropolis sampling is not well-suited for situations where energy and force evaluations are computationally *** search for a more efficient technique,we here explore the performance of Hybrid Monte Carlo sampling,an algorithm widely used in quantum electrodynamics,as a structure prediction scheme for systems with long-range *** results show that the Hybrid Monte Carlo algorithm stands out as an excellent computational scheme that can not only significantly outperform the Metropolis sampling but also complement molecular dynamics in materials science applications,while allowing ultra-large-scale simulations of systems containing millions of particles.

关键词： prediction property scheme

Beginning from the end:the presynaptic terminal as a pathomechanism hub in frontotemporal dementia and amyotrophic lateral sclerosis

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Neural Regeneration Research 2025年第11期20卷 3217-3218页

作者： laura Huggon Emma l.Clayton UK Dementia Research Institute at King’s College london LondonUK Department of Basic and Clinical Neuroscience Institute of Psychiatry Psychology&NeuroscienceKing’s College LondonLondonUK

Frontotemporal dementia and amyotrophic lateral sclerosis:Frontotemporal dementia(F T D)and amyo t rophic lateral sclerosis(AlS)are neurodegenerative diseases with significant overlapping *** these neurodegenerative diseases affect different neuronal populations(with FTD affecting neurons of the frontal and temporal lobes,and AlS affecting upper and lower motor neurons),these two diseases are complexly *** and AlS exist on a disease spectrum,with shared genetic causes,clinical presentations,and pathologies.

关键词： diseases amyotrophic sclerosis

Strain-induced resonances in the dynamical quadratic magnetoelectric response of multiferroics

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npj Computational Materials 2020年第1期6卷 1156-1161页

作者： S.Omid Sayedaghaee Charles Paillard Sergey Prosandeev Bin Xu laurent bellaiche Physics Department and Institute for Nanoscience and Engineering University of ArkansasFayettevilleArkansas 72701USA Microelectronics-Photonics Program University of ArkansasFayettevilleArkansas 72701USA laboratoire Structures Propriétés et Modélisation des SolidesCentraleSupélecCNRS UMR 8580UniversitéParis-Saclay91190 Gifsur-YvetteFrance Institute of Physics and Physics Department of Southern Federal University Rostov-na-Donu 344090Russia School of Physical Science and Technology Soochow UniversitySuzhouJiangsu 215006China

For the last few years,the research interest in magnetoelectric(ME)effect,which is the cross-coupling between ferroelectric and magnetic ordering in multiferroic materials,has experienced a significant *** extensive recent studies are not only conducted towards the design of sensors,actuators,transducers,and memory devices by taking advantage of the cross-control of polarization(or magnetization)by magnetic(or electric)fields,but also aim to create a clearer picture in understanding the sources of ME responses and the novel effects associated with *** we derive analytical models allowing to understand the striking and novel dynamics of ME effects in multiferroics and further confirm it with atomistic ***,the role of strain is revealed to lead to the existence of electroacoustic magnons,a new quasiparticle that mixes acoustic and optical phonons with magnons,which results in resonances and thus a dramatic enhancement of magnetoelectric ***,a unique aspect of the dynamical quadratic ME response under a magnetic field with varying frequencies,which is the second harmonic generation(SHG),has not been discussed prior to the present *** SHGs put emphasis on the fact that nonlinearities should be considered while dealing with such systems.

关键词： quadratic dynamical resonance