Quantum material systems upon applying ultrashort laser pulses provide a rich platform to access excited material phases and their transformations that are not entirely like their equilibrium counterparts. The addressability and potential controls of metastable or long-trapped out-of-equilibrium phases have motivated interests both for the purposes of understanding the nonequilibrium physics and advancing the quantum technologies. Thus far, the dynamical spectroscopic probes eminently focus on microscopic electronic and phonon responses. For characterizing the long-range dynamics, such as order parameter fields and fluctuation effects, the ultrafast scattering probes offer direct sensitivity. Bridging the connections between the microscopic dynamics and macroscopic responses is central toward establishing the nonequilibrium physics behind the light-induced phases. Here, we present a path toward such understanding by cross-examining the structure factors associated with different dynamical states obtained from ultrafast electron scattering, imaging, and modeling. We give the basic theoretical framework on describing the non-equilibrium scattering problems and briefly describe how such framework relates to the out-of-equilibrium phenomena. We give effective models outlining the emergences of nonthermal critical points, hidden phases, and non-equilibrium relaxational responses from vacuum-suspended rare-earth tritellurides, tantalum disulfides thin films, and vanadium dioxide nanocrystalline materials upon light excitations.
{"title":"Toward nonthermal control of excited quantum materials: framework and investigations by ultrafast electron scattering and imaging","authors":"Xiaoyi Sun, Shuaishuai Sun, Chong-Yu Ruan","doi":"10.5802/crphys.86","DOIUrl":"https://doi.org/10.5802/crphys.86","url":null,"abstract":"Quantum material systems upon applying ultrashort laser pulses provide a rich platform to access excited material phases and their transformations that are not entirely like their equilibrium counterparts. The addressability and potential controls of metastable or long-trapped out-of-equilibrium phases have motivated interests both for the purposes of understanding the nonequilibrium physics and advancing the quantum technologies. Thus far, the dynamical spectroscopic probes eminently focus on microscopic electronic and phonon responses. For characterizing the long-range dynamics, such as order parameter fields and fluctuation effects, the ultrafast scattering probes offer direct sensitivity. Bridging the connections between the microscopic dynamics and macroscopic responses is central toward establishing the nonequilibrium physics behind the light-induced phases. Here, we present a path toward such understanding by cross-examining the structure factors associated with different dynamical states obtained from ultrafast electron scattering, imaging, and modeling. We give the basic theoretical framework on describing the non-equilibrium scattering problems and briefly describe how such framework relates to the out-of-equilibrium phenomena. We give effective models outlining the emergences of nonthermal critical points, hidden phases, and non-equilibrium relaxational responses from vacuum-suspended rare-earth tritellurides, tantalum disulfides thin films, and vanadium dioxide nanocrystalline materials upon light excitations.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43530971","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}
A. Mussi, P. Carrez, K. Gouriet, B. Hue, P. Cordier
Imaging dislocation microstructures in 3D and monitoring their interactions over time is a major challenge. In this study, we show that enhancing the contrast of dislocation lines prior to reconstruction, allows to optimize an acquisition phase with fewer images and thus to follow the 3D evolution of a microstructure over time. We illustrate this new possibility by studying the first stages of formation of helical dislocations in MgO under electron irradiation. We highlight the role of segment mobility on the initiation of climb and reveal the existence of preferential mixed climb planes.
{"title":"4D electron tomography of dislocations undergoing electron irradiation","authors":"A. Mussi, P. Carrez, K. Gouriet, B. Hue, P. Cordier","doi":"10.5802/crphys.80","DOIUrl":"https://doi.org/10.5802/crphys.80","url":null,"abstract":"Imaging dislocation microstructures in 3D and monitoring their interactions over time is a major challenge. In this study, we show that enhancing the contrast of dislocation lines prior to reconstruction, allows to optimize an acquisition phase with fewer images and thus to follow the 3D evolution of a microstructure over time. We illustrate this new possibility by studying the first stages of formation of helical dislocations in MgO under electron irradiation. We highlight the role of segment mobility on the initiation of climb and reveal the existence of preferential mixed climb planes.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46019754","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}
R. Gautier, Armin Rajabzadeh, M. Larranaga, N. Combe, F. Mompiou, M. Legros
Grain size reduction is a very efficient way to block dislocation movements and therefore create very strong metals and alloys. Not only grain boundaries are known obstacles for dislocations, but when reaching nanometer dimensions, crystallites usually become dislocation free, which imposes an additional constraint to develop plasticity. A recent effort to understand grain boundaries-based deformation mechanisms has therefore emerged. These mechanisms can be manifold, involving conservative and diffusive processes that are very poorly understood. A first approach consisting in downscaling mechanisms that are documented at large scale such as Coble creep, proved very limited. On the other hand, stress-assisted grain growth or shear-coupled grain boundary migration, that were recently observed in small-grained materials at room or low temperature may provide a crucial step to fully understand dislocation-less plasticity in nanocrystals. As this is a completely new field with many more degrees of freedom, a continuous research effort has to be carried out to link the mechanical properties of nanocrystals to these mechanisms specifically linked to grain boundaries. Résumé. La réduction de la taille des grains est un moyen très efficace de bloquer les mouvements de dislocations et donc d’augmenter la résistance mécanique des métaux et alliages. Non seulement les joints de ∗Corresponding author. ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/ 2 Romain Gautier et al. grains sont des obstacles connus pour les dislocations, mais lorsqu’ils atteignent des dimensions nanométriques, les cristallites deviennent généralement vides de dislocations, ce qui impose une contrainte supplémentaire pour développer la plasticité. Comprendre les mécanismes de déformation basés sur les joints de grains est devenu un enjeu majeur de la métallurgie physique. Ces mécanismes peuvent être multiples, impliquant des processus conservatifs et diffusifs qui sont mal compris. Une première approche qui consiste à transposer aux petites dimensions des mécanismes documentés à grande échelle comme le fluage de Coble, s’est avérée très limitée. Au contraire, la croissance des grains assistée par la contrainte ou la migration des joints de grains couplée au cisaillement, récemment observées dans les matériaux à petits grains à température ambiante, peuvent fournir une clé pour comprendre pleinement la “plasticité sans dislocation” dans les nanocristaux. Comme il s’agit d’un domaine relativement nouveau avec beaucoup plus de degrés de liberté, un effort de recherche continu doit être mené pour relier les propriétés mécaniques des nanocristaux à ces processus de plasticité basés sur les joints de grains.
减小晶粒尺寸是阻止位错运动的一种非常有效的方法，因此可以制造出非常坚固的金属和合金。众所周知，不仅晶界是位错的障碍，而且当达到纳米尺寸时，晶体通常变得无位错，这对塑性的发展施加了额外的限制。因此，最近出现了一种理解基于晶界的变形机制的努力。这些机制可以是多种多样的，包括保守和扩散过程，但人们对这些过程知之甚少。第一种方法包括在大尺度上记录的缩小机制，如Coble蠕变，被证明是非常有限的。另一方面，最近在室温或低温下在小晶粒材料中观察到的应力辅助晶粒生长或剪切耦合晶界迁移，可能为充分理解纳米晶体的无位错塑性提供了关键的一步。由于这是一个具有更多自由度的全新领域，因此必须进行持续的研究工作，以将纳米晶体的机械特性与这些具体与晶界相关的机制联系起来。的简历。“变变”的意思是“变变”，“变变”的意思是“变变”，“变变”的意思是“变变”，“变变”的意思是“变变”。非沉降les关节de *通讯作者。[电子版]:1878-1535 https://comptes-rendus.academie-sciences.fr/physique/ [2] Romain Gautier等。晶粒结构的障碍、孔洞、孔洞、孔洞、孔洞、孔洞、孔洞、孔洞、孔洞和孔洞。理解les msamcanismes de dsamicformass - ssamicass - s关节de grains - devenu - enjeu majeur de la msamicasturgie体格。这两种类型的变异体能防止être倍数，隐含的变异体过程的保守性和扩散性相当不正常。一种主要的办法是:将小尺寸的数据转换为文件，将小尺寸的数据转换为文件，将大尺寸的数据转换为文件，将小尺寸的数据转换为文件，将小尺寸的数据转换为有限尺寸的数据。与此相反，谷物的混合有助于防止谷物的混合迁移;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;谷物的混合迁移与谷物的混合迁移耦合;Comme ' s agit d 'un domain关系nouveau avecoup和de degracreches de libertest, uneffort de recherche continu doit être menmenede pour relier les les grime me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me。
{"title":"Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?","authors":"R. Gautier, Armin Rajabzadeh, M. Larranaga, N. Combe, F. Mompiou, M. Legros","doi":"10.5802/crphys.52","DOIUrl":"https://doi.org/10.5802/crphys.52","url":null,"abstract":"Grain size reduction is a very efficient way to block dislocation movements and therefore create very strong metals and alloys. Not only grain boundaries are known obstacles for dislocations, but when reaching nanometer dimensions, crystallites usually become dislocation free, which imposes an additional constraint to develop plasticity. A recent effort to understand grain boundaries-based deformation mechanisms has therefore emerged. These mechanisms can be manifold, involving conservative and diffusive processes that are very poorly understood. A first approach consisting in downscaling mechanisms that are documented at large scale such as Coble creep, proved very limited. On the other hand, stress-assisted grain growth or shear-coupled grain boundary migration, that were recently observed in small-grained materials at room or low temperature may provide a crucial step to fully understand dislocation-less plasticity in nanocrystals. As this is a completely new field with many more degrees of freedom, a continuous research effort has to be carried out to link the mechanical properties of nanocrystals to these mechanisms specifically linked to grain boundaries. Résumé. La réduction de la taille des grains est un moyen très efficace de bloquer les mouvements de dislocations et donc d’augmenter la résistance mécanique des métaux et alliages. Non seulement les joints de ∗Corresponding author. ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/ 2 Romain Gautier et al. grains sont des obstacles connus pour les dislocations, mais lorsqu’ils atteignent des dimensions nanométriques, les cristallites deviennent généralement vides de dislocations, ce qui impose une contrainte supplémentaire pour développer la plasticité. Comprendre les mécanismes de déformation basés sur les joints de grains est devenu un enjeu majeur de la métallurgie physique. Ces mécanismes peuvent être multiples, impliquant des processus conservatifs et diffusifs qui sont mal compris. Une première approche qui consiste à transposer aux petites dimensions des mécanismes documentés à grande échelle comme le fluage de Coble, s’est avérée très limitée. Au contraire, la croissance des grains assistée par la contrainte ou la migration des joints de grains couplée au cisaillement, récemment observées dans les matériaux à petits grains à température ambiante, peuvent fournir une clé pour comprendre pleinement la “plasticité sans dislocation” dans les nanocristaux. Comme il s’agit d’un domaine relativement nouveau avec beaucoup plus de degrés de liberté, un effort de recherche continu doit être mené pour relier les propriétés mécaniques des nanocristaux à ces processus de plasticité basés sur les joints de grains.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42461103","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}
Vanadium dioxide exhibits a first order metal to insulator transition (MIT) at 340 K (TMI) from a rutile (R) structure to a monoclinic (M1) structure. The mechanism of this transition interpreted as due either to a Peierls instability or to a Mott–Hubbard instability is controversial since half a century. However, in the last twenty years the study of chemical and physical properties of VO2 and of its alloys, benefits of a renewed interest due to possible applications coming from the realization of devices made of thin films. We describe in this review the structural, electronic and magnetic properties of the different metallic (R) and insulating (M1, T, M2) phases of VO2, of its solid solutions and under constraint. We present in a synthetic manner the various phase diagrams and their symmetry analysis. This work allows us to revisit older interpretation and to emphasize in particular the combined role of electron–electron interactions in the various phase of VO2 and of structural fluctuations in the MIT mechanism. In this framework we show that the phase transition is surprisingly announced by anisotropic one-dimensional (1D) structural fluctuations revealing chain like correlations between the V due to an incipient instability of the rutile structure. This leads to an unexpected critical dynamics of the order–disorder (or relaxation) type. We describe how the two-dimensional (2D) coupling between these 1D fluctuations, locally forming uniform V4+ zig-zag chains and V–V pairs, stabilizes the M2 and M1 insulating phases. These phases exhibit a 1D electronic anisotropy where substantial electron–electron correlations conduct to a spin–charge decoupling. The spin-Peierls ground state of M1 is analyzed via a mechanism of dimerization, in the T phase, of the spin 1/2 V 4+ zigzag Heisenberg chains formed in the M2 phase. This review summarizes in a critical manner the main results of the large literature on fundamental aspects of the MIT of VO2. It is completed by unpublished old results. Interpretations are also placed in a large conceptual frame which is also relevant to interpret physical properties of other classes of materials. Résumé. Le dioxyde de vanadium présente une transition métal–isolant (TMI) du premier ordre à 340 K (=TMI) d’une structure rutile (R) à une structure monoclinique (M1). Le mécanisme de cette transition interprétée comme étant due soit à une instabilité de Peierls soit à une instabilité de Mott–Hubbard reste très controversé depuis près d’un demi-siècle. Cependant depuis une vingtaine d’années l’étude des propriétés chimiques et physiques de VO2 et de ses alliages suscite un renouveau d’intérêt par la possibilité d’applications provenant de l’obtention de dispositifs s’appuyant sur la réalisation de films minces. Nous décrivons dans cette revue les propriétés structurales, électroniques et magnétiques des différentes phases métallique ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/
在340 K (TMI)温度下，二氧化钒表现出从金红石(R)结构到单斜晶(M1)结构的一阶金属到绝缘体转变(MIT)。这种转变的机制被解释为由于佩尔斯不稳定性或莫特-哈伯德不稳定性，半个世纪以来一直存在争议。然而，在过去的二十年中，对氧化钨及其合金的化学和物理性质的研究，由于可能的应用来自于薄膜器件的实现而重新引起了人们的兴趣。本文描述了VO2的不同金属相(R)和绝缘相(M1, T, M2)、固溶体和约束条件下的结构、电子和磁性能。我们以综合的方式给出了各种相图及其对称性分析。这项工作使我们能够重新审视旧的解释，并特别强调电子-电子相互作用在VO2的各个阶段和MIT机制中的结构波动的综合作用。在这个框架中，我们证明了相变是由各向异性的一维(1D)结构波动出人意料地宣布的，揭示了由于金红石结构的早期不稳定性而导致的V之间的链状相关性。这导致了一种意想不到的有序-无序(或松弛)类型的临界动态。我们描述了这些一维波动之间的二维(2D)耦合如何在局部形成均匀的V4+之字形链和V-V对，从而稳定M2和M1绝缘相。这些相表现出一维电子各向异性，其中大量的电子-电子相关导致自旋-电荷去耦。通过M2相中形成的自旋1/ 2v4 +之字形海森堡链在T相中二聚化的机制，分析了M1的自旋-佩尔斯基态。这篇综述以一种批判性的方式总结了关于VO2的MIT基本方面的大量文献的主要结果。它是由未发表的旧结果完成的。解释也被置于一个大的概念框架中，这也与解释其他类别材料的物理性质有关。的简历。二氧化钒的单晶过渡单晶隔离(TMI) du premier order: 340k (=TMI)，单晶结构金红石(R)，单晶结构单晶(M1)。Le macimcanisme de cette transition interpracimetacme comcomtant due soit une instability . de peerls soit une instability . de mot - hubbard restere tris有争议的suispris d 'un demi- si。Cependant从一个vingtaine d 'annees我des proprietes chimiques等最大的体格不吸烟者ses alliages suscite联合国renouveau有票面拉一d 'applications provenant de l 'obtention de dispositifs年代'appuyant在洛杉矶认识电影切碎。Nous dsamrivons dans cette revue les propriacematsames strucales，电子的samriques和不同的samriques des different samrites phases .(电子版):1878-1535 https://comptes-rendus.academie-sciences.fr/physique/
{"title":"Basic aspects of the metal–insulator transition in vanadium dioxide VO 2 : a critical review","authors":"J. Pouget","doi":"10.5802/CRPHYS.74","DOIUrl":"https://doi.org/10.5802/CRPHYS.74","url":null,"abstract":"Vanadium dioxide exhibits a first order metal to insulator transition (MIT) at 340 K (TMI) from a rutile (R) structure to a monoclinic (M1) structure. The mechanism of this transition interpreted as due either to a Peierls instability or to a Mott–Hubbard instability is controversial since half a century. However, in the last twenty years the study of chemical and physical properties of VO2 and of its alloys, benefits of a renewed interest due to possible applications coming from the realization of devices made of thin films. We describe in this review the structural, electronic and magnetic properties of the different metallic (R) and insulating (M1, T, M2) phases of VO2, of its solid solutions and under constraint. We present in a synthetic manner the various phase diagrams and their symmetry analysis. This work allows us to revisit older interpretation and to emphasize in particular the combined role of electron–electron interactions in the various phase of VO2 and of structural fluctuations in the MIT mechanism. In this framework we show that the phase transition is surprisingly announced by anisotropic one-dimensional (1D) structural fluctuations revealing chain like correlations between the V due to an incipient instability of the rutile structure. This leads to an unexpected critical dynamics of the order–disorder (or relaxation) type. We describe how the two-dimensional (2D) coupling between these 1D fluctuations, locally forming uniform V4+ zig-zag chains and V–V pairs, stabilizes the M2 and M1 insulating phases. These phases exhibit a 1D electronic anisotropy where substantial electron–electron correlations conduct to a spin–charge decoupling. The spin-Peierls ground state of M1 is analyzed via a mechanism of dimerization, in the T phase, of the spin 1/2 V 4+ zigzag Heisenberg chains formed in the M2 phase. This review summarizes in a critical manner the main results of the large literature on fundamental aspects of the MIT of VO2. It is completed by unpublished old results. Interpretations are also placed in a large conceptual frame which is also relevant to interpret physical properties of other classes of materials. Résumé. Le dioxyde de vanadium présente une transition métal–isolant (TMI) du premier ordre à 340 K (=TMI) d’une structure rutile (R) à une structure monoclinique (M1). Le mécanisme de cette transition interprétée comme étant due soit à une instabilité de Peierls soit à une instabilité de Mott–Hubbard reste très controversé depuis près d’un demi-siècle. Cependant depuis une vingtaine d’années l’étude des propriétés chimiques et physiques de VO2 et de ses alliages suscite un renouveau d’intérêt par la possibilité d’applications provenant de l’obtention de dispositifs s’appuyant sur la réalisation de films minces. Nous décrivons dans cette revue les propriétés structurales, électroniques et magnétiques des différentes phases métallique ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":"8 1","pages":"37-87"},"PeriodicalIF":1.4,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86913361","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}
Lei Ren, C. Robert, B. Urbaszek, X. Marie, M. A. Semina, M. Glazov
. We review the physical mechanisms that allow tuning of absorption and emission characteristics in monolayer semiconductors. We use the model system of transition metal dichalcogenide mono-layers such as MoSe 2 or WSe 2 due to their very e ffi cient light-matter interaction and availability of high quality samples. For monolayers encapsulated in hexagonal boron nitride both homogeneous and inhomogenous contributions to the exciton optical transition linewidth can be tuned opening up pathways for tailoring the reflectivity and absorption in van der Waals heterostructures
{"title":"Tuning absorption and emission in monolayer semiconductors: a brief survey","authors":"Lei Ren, C. Robert, B. Urbaszek, X. Marie, M. A. Semina, M. Glazov","doi":"10.5802/CRPHYS.59","DOIUrl":"https://doi.org/10.5802/CRPHYS.59","url":null,"abstract":". We review the physical mechanisms that allow tuning of absorption and emission characteristics in monolayer semiconductors. We use the model system of transition metal dichalcogenide mono-layers such as MoSe 2 or WSe 2 due to their very e ffi cient light-matter interaction and availability of high quality samples. For monolayers encapsulated in hexagonal boron nitride both homogeneous and inhomogenous contributions to the exciton optical transition linewidth can be tuned opening up pathways for tailoring the reflectivity and absorption in van der Waals heterostructures","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43774937","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}
We present here a small review on our exhaustive theoretical study of point defects in a MoS2 monolayer. Using Density Functional Theory (DFT), we characterize structurally and electronically different kinds of defects based on S and Mo vacancies, as well as their antisites. In combination with a Keldysh–Green formalism, we model the corresponding Scanning Tunneling Microscopy (STM) images. Also, we determine the forces to be compared with Atomic Force Microscopy (AFM) measurements, and explore the possibilities of molecular adsorption. Our method, as a support to experimental measurements allows to clearly discriminate the different types of defects. Finally, we present very recent results on lateral conductance calculations of defective MoS2 nanoribbons. All these findings pave the way to novel applications in nanoelectronics or gas sensors, and show the need to further explore these new systems. Résumé. Nous présentons ici une mini-revue de nos différents travaux sur l’étude théorique des défauts dans une monocouche de MoS2. En utilisant la Théorie de la Fonctionnelle de la Densité (DFT), nous avons caractérisé structurellement et électroniquement différents types de défauts à partir de lacunes de S et Mo, ainsi que leurs antisites. En combinaison avec un formalisme de Green–Keldysh, nous avons simulé les images de microscopie à effet tunnel (STM) correspondantes. Egalement, nous avons déterminé les forces, ∗Corresponding authors. ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/ 2 César González and Yannick J. Dappe afin d’interpréter les expériences de microscopie à force atomique (AFM). Nous avons également étudié l’adsorption de molécules sur ces défauts. Finalement, nous présentons de récents résultats sur le calcul de conductance latérale dans des nano-rubans de MoS2 avec défauts. Ces travaux ouvrent la voie à de nouvelles applications en nanoélectronique ou pour les capteurs de gaz, et soulignent la nécessité d’explorer plus avant ces nouveaux systèmes.
{"title":"Theoretical approach to point defects in a single transition metal dichalcogenide monolayer: conductance and force calculations in MoS 2","authors":"César González, Y. Dappe","doi":"10.5802/CRPHYS.72","DOIUrl":"https://doi.org/10.5802/CRPHYS.72","url":null,"abstract":"We present here a small review on our exhaustive theoretical study of point defects in a MoS2 monolayer. Using Density Functional Theory (DFT), we characterize structurally and electronically different kinds of defects based on S and Mo vacancies, as well as their antisites. In combination with a Keldysh–Green formalism, we model the corresponding Scanning Tunneling Microscopy (STM) images. Also, we determine the forces to be compared with Atomic Force Microscopy (AFM) measurements, and explore the possibilities of molecular adsorption. Our method, as a support to experimental measurements allows to clearly discriminate the different types of defects. Finally, we present very recent results on lateral conductance calculations of defective MoS2 nanoribbons. All these findings pave the way to novel applications in nanoelectronics or gas sensors, and show the need to further explore these new systems. Résumé. Nous présentons ici une mini-revue de nos différents travaux sur l’étude théorique des défauts dans une monocouche de MoS2. En utilisant la Théorie de la Fonctionnelle de la Densité (DFT), nous avons caractérisé structurellement et électroniquement différents types de défauts à partir de lacunes de S et Mo, ainsi que leurs antisites. En combinaison avec un formalisme de Green–Keldysh, nous avons simulé les images de microscopie à effet tunnel (STM) correspondantes. Egalement, nous avons déterminé les forces, ∗Corresponding authors. ISSN (electronic) : 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/ 2 César González and Yannick J. Dappe afin d’interpréter les expériences de microscopie à force atomique (AFM). Nous avons également étudié l’adsorption de molécules sur ces défauts. Finalement, nous présentons de récents résultats sur le calcul de conductance latérale dans des nano-rubans de MoS2 avec défauts. Ces travaux ouvrent la voie à de nouvelles applications en nanoélectronique ou pour les capteurs de gaz, et soulignent la nécessité d’explorer plus avant ces nouveaux systèmes.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42235114","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}
Nanoparticles are commonly used in various fields of applications such as electronics, catalysis or engineering where they can be subjected to a certain amount of stress leading to structural instabilities or irreversible damages. In contrast with bulk materials, nanoparticles can sustain extremely high stresses (in the GPa range) and ductility, even in the case of originally brittle materials. This review article focuses on the modeling of the mechanical properties of nanoparticles, with an emphasis on elementary deformation processes. Various simulation methods are described, from classical molecular dynamics calculations, the best suited method when applied to the modeling the mechanics of nanoparticles, to dislocation dynamics based hybrid methodologies. We detail the mechanical behaviour of nanoparticles for a large array of material classes (metals, semi-conductors, ceramics, etc.), as well as their deformation processes. Regular crystalline nanoparticles are addressed, as well as more complex systems such as nanoporous or core-shell particles. In addition to the exhaustive review on the recent works published on the topic, challenges and future trends are proposed, providing solid foundations for forthcoming investigations.
{"title":"Modeling the mechanical properties of nanoparticles: a review","authors":"J. Amodeo, L. Pizzagalli","doi":"10.5802/CRPHYS.70","DOIUrl":"https://doi.org/10.5802/CRPHYS.70","url":null,"abstract":"Nanoparticles are commonly used in various fields of applications such as electronics, catalysis or engineering where they can be subjected to a certain amount of stress leading to structural instabilities or irreversible damages. In contrast with bulk materials, nanoparticles can sustain extremely high stresses (in the GPa range) and ductility, even in the case of originally brittle materials. This review article focuses on the modeling of the mechanical properties of nanoparticles, with an emphasis on elementary deformation processes. Various simulation methods are described, from classical molecular dynamics calculations, the best suited method when applied to the modeling the mechanics of nanoparticles, to dislocation dynamics based hybrid methodologies. We detail the mechanical behaviour of nanoparticles for a large array of material classes (metals, semi-conductors, ceramics, etc.), as well as their deformation processes. Regular crystalline nanoparticles are addressed, as well as more complex systems such as nanoporous or core-shell particles. In addition to the exhaustive review on the recent works published on the topic, challenges and future trends are proposed, providing solid foundations for forthcoming investigations.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":"30 1","pages":"1-32"},"PeriodicalIF":1.4,"publicationDate":"2021-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79653764","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}
E. Clouet, Baptiste Bienvenu, L. Dezerald, D. Rodney
We show here how density functional theory calculations can be used to predict the temperatureand orientation-dependence of the yield stress of body-centered cubic (BCC) metals in the thermallyactivated regime where plasticity is governed by the glide of screw dislocations with a 1/2 Burgers vector. Our numerical model incorporates non-Schmid effects, both the twinning/antitwinning asymmetry and non-glide effects, characterized through ab initio calculations on straight dislocations. The model uses the stress-dependence of the kink-pair nucleation enthalpy predicted by a line tension model also fully parameterized on ab initio calculations. The methodology is illustrated here on BCC tungsten but is applicable to all BCC metals. Comparison with experimental data allows to highlight both the successes and remaining limitations of our modeling approach.
{"title":"Screw dislocations in BCC transition metals: from ab initio modeling to yield criterion","authors":"E. Clouet, Baptiste Bienvenu, L. Dezerald, D. Rodney","doi":"10.5802/CRPHYS.75","DOIUrl":"https://doi.org/10.5802/CRPHYS.75","url":null,"abstract":"We show here how density functional theory calculations can be used to predict the temperatureand orientation-dependence of the yield stress of body-centered cubic (BCC) metals in the thermallyactivated regime where plasticity is governed by the glide of screw dislocations with a 1/2 Burgers vector. Our numerical model incorporates non-Schmid effects, both the twinning/antitwinning asymmetry and non-glide effects, characterized through ab initio calculations on straight dislocations. The model uses the stress-dependence of the kink-pair nucleation enthalpy predicted by a line tension model also fully parameterized on ab initio calculations. The methodology is illustrated here on BCC tungsten but is applicable to all BCC metals. Comparison with experimental data allows to highlight both the successes and remaining limitations of our modeling approach.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43783717","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}
G. Gougeon, Y. Corre, Mohammed Zahid Aslam, Simon Bicais, Jean-Baptiste Doré
Spectrum above 90 GHz is a promising investigation domain to offer future wireless networks with performance beyond IMT 2020 such as 100+ Gbit/s data rate or sub-ms latency. In particular, the huge available bandwidth can serve the backhaul transport network in the perspective of future ultra-dense deployments, and massive front-haul data streams. This paper investigates the feasibility and characteristics of the in-street sub-THz mesh backhauling. The study relies on the highly realistic simulation of the physical layer performance, based on detailed geographical representation, ray-based propagation modelling, RF phase noise impairment, and a new modulation scheme robust to phase noise. The achievable throughput is studied, and it is shown that each link of a dense mesh backhaul network can reliably deliver several Gbit/s per 1-GHz carrier bandwidth. The multi-path diversity is assessed, as well as the impact of rainfall and phase noise level.
{"title":"Investigating sub-THz PHY layer for future high-data-rate wireless backhaul","authors":"G. Gougeon, Y. Corre, Mohammed Zahid Aslam, Simon Bicais, Jean-Baptiste Doré","doi":"10.5802/CRPHYS.66","DOIUrl":"https://doi.org/10.5802/CRPHYS.66","url":null,"abstract":"Spectrum above 90 GHz is a promising investigation domain to offer future wireless networks with performance beyond IMT 2020 such as 100+ Gbit/s data rate or sub-ms latency. In particular, the huge available bandwidth can serve the backhaul transport network in the perspective of future ultra-dense deployments, and massive front-haul data streams. This paper investigates the feasibility and characteristics of the in-street sub-THz mesh backhauling. The study relies on the highly realistic simulation of the physical layer performance, based on detailed geographical representation, ray-based propagation modelling, RF phase noise impairment, and a new modulation scheme robust to phase noise. The achievable throughput is studied, and it is shown that each link of a dense mesh backhaul network can reliably deliver several Gbit/s per 1-GHz carrier bandwidth. The multi-path diversity is assessed, as well as the impact of rainfall and phase noise level.","PeriodicalId":50650,"journal":{"name":"Comptes Rendus Physique","volume":"37 1","pages":"1-11"},"PeriodicalIF":1.4,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81214559","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}
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