Pub Date : 2024-12-19DOI: 10.1038/s42005-024-01861-w
Joseph Vimal Vas, Rohit Medwal, Sourabh Manna, Mayank Mishra, Aaron Muller, John Rex Mohan, Yasuhiro Fukuma, Martial Duchamp, Rajdeep Singh Rawat
Controlling the magnetic domain propagation is the key to realize ultrafast, high-density domain wall-based memory and logic devices for next generation computing. Two-Dimensional (2D) Van der Waals materials introduce localized modifications to the interfacial magnetic order, which could enable efficient control over the propagation of magnetic domains. However, there is limited direct experimental evidence and understanding of the underlying mechanism, for 2D material mediated control of domain wall propagation. Here, using Lorentz-Transmission Electron Microscopy (L-TEM) along with the Modified Transport of Intensity equations (MTIE), we demonstrate controlled domain expansion with in-situ magnetic field in a ferromagnet (Permalloy, NiFe) interfacing with a 2D VdW material Graphene (Gr). The Gr/NiFe interface exhibits distinctive domain expansion rate with magnetic field selectively near the interface which is further analysed using micromagnetic simulations. Our findings are crucial for comprehending direct visualization of interface controlled magnetic domain expansion, offering insights for developing future domain wall-based technology. This study explores how the interface between Permalloy and graphene affects the propagation of magnetic domains. Using advanced transmission electron microscopy and simulations, the research reveals key insights that could advance future memory and logic technologies.
{"title":"Direct visualization of local magnetic domain dynamics in a 2D Van der Walls material/ferromagnet interface","authors":"Joseph Vimal Vas, Rohit Medwal, Sourabh Manna, Mayank Mishra, Aaron Muller, John Rex Mohan, Yasuhiro Fukuma, Martial Duchamp, Rajdeep Singh Rawat","doi":"10.1038/s42005-024-01861-w","DOIUrl":"10.1038/s42005-024-01861-w","url":null,"abstract":"Controlling the magnetic domain propagation is the key to realize ultrafast, high-density domain wall-based memory and logic devices for next generation computing. Two-Dimensional (2D) Van der Waals materials introduce localized modifications to the interfacial magnetic order, which could enable efficient control over the propagation of magnetic domains. However, there is limited direct experimental evidence and understanding of the underlying mechanism, for 2D material mediated control of domain wall propagation. Here, using Lorentz-Transmission Electron Microscopy (L-TEM) along with the Modified Transport of Intensity equations (MTIE), we demonstrate controlled domain expansion with in-situ magnetic field in a ferromagnet (Permalloy, NiFe) interfacing with a 2D VdW material Graphene (Gr). The Gr/NiFe interface exhibits distinctive domain expansion rate with magnetic field selectively near the interface which is further analysed using micromagnetic simulations. Our findings are crucial for comprehending direct visualization of interface controlled magnetic domain expansion, offering insights for developing future domain wall-based technology. This study explores how the interface between Permalloy and graphene affects the propagation of magnetic domains. Using advanced transmission electron microscopy and simulations, the research reveals key insights that could advance future memory and logic technologies.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-6"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01861-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-19DOI: 10.1038/s42005-024-01863-8
Aydin Ashrafi-Belgabad, Reza Karimi, Mohammad Monfared, Kaili Tian, Parviz Parvin, Benji Wales, Éric Bisson, Samuel Beaulieu, Mathieu Giguère, Jean-Claude Kieffer, Philippe Lassonde, François Légaré, Heide Ibrahim, Joseph H. Sanderson
Coulomb explosion is an established momentum imaging technique, where the molecules are ionized multiple times on a femtosecond time scale before breaking up into ionized fragments. By measuring the momentum of all the ions, information about the initial molecular structure is theoretically available. However, significant geometric changes due to multiple ionizations occur before the explosion, posing a challenge in retrieving the ground-state structure of molecules from the measured momentum values of the fragments. In this work, we investigate theoretically and experimentally such a connection between the ground-state geometry of a polyatomic molecule (OCS) and the detected momenta of ionic fragments from the Coulomb explosion. By relying on time-dependent density functional theory (TDDFT), we can rigorously model the ionization dynamics of the molecule in the tunneling regime. We reproduce the energy release and the Newton plot momentum patterns of an experiment in which OCS is ionized to the 6+ charge state. Our results provide insight into the behavior of molecules during strong field multiple ionization, opening a way toward precision imaging of real-space molecular geometries using tabletop lasers. Understanding molecular structure and dynamics through strong-field laser interactions holds great promise. The authors use quantum calculations to show how bonds and angles evolve in an OCS molecule ionized six times by a 7 fs, 800 nm laser pulse, accurately predicting our experimental results.
{"title":"Reconstructing real-space geometries of polyatomic molecules undergoing strong field laser-induced Coulomb explosion","authors":"Aydin Ashrafi-Belgabad, Reza Karimi, Mohammad Monfared, Kaili Tian, Parviz Parvin, Benji Wales, Éric Bisson, Samuel Beaulieu, Mathieu Giguère, Jean-Claude Kieffer, Philippe Lassonde, François Légaré, Heide Ibrahim, Joseph H. Sanderson","doi":"10.1038/s42005-024-01863-8","DOIUrl":"10.1038/s42005-024-01863-8","url":null,"abstract":"Coulomb explosion is an established momentum imaging technique, where the molecules are ionized multiple times on a femtosecond time scale before breaking up into ionized fragments. By measuring the momentum of all the ions, information about the initial molecular structure is theoretically available. However, significant geometric changes due to multiple ionizations occur before the explosion, posing a challenge in retrieving the ground-state structure of molecules from the measured momentum values of the fragments. In this work, we investigate theoretically and experimentally such a connection between the ground-state geometry of a polyatomic molecule (OCS) and the detected momenta of ionic fragments from the Coulomb explosion. By relying on time-dependent density functional theory (TDDFT), we can rigorously model the ionization dynamics of the molecule in the tunneling regime. We reproduce the energy release and the Newton plot momentum patterns of an experiment in which OCS is ionized to the 6+ charge state. Our results provide insight into the behavior of molecules during strong field multiple ionization, opening a way toward precision imaging of real-space molecular geometries using tabletop lasers. Understanding molecular structure and dynamics through strong-field laser interactions holds great promise. The authors use quantum calculations to show how bonds and angles evolve in an OCS molecule ionized six times by a 7 fs, 800 nm laser pulse, accurately predicting our experimental results.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01863-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-19DOI: 10.1038/s42005-024-01892-3
Gustavo Chaparro, Erich A. Müller
A longstanding challenge in thermodynamics has been the development of a unified analytical expression for the free energy of matter capable of describing all thermodynamic properties. Although significant strides have been made in modeling fluid phases using continuous equations of state (EoSs), the crystalline state has remained largely unexplored because of its complexity. This work introduces an approach that employs artificial neural networks to construct an EoS directly from comprehensive molecular simulation data. The efficacy of this method is demonstrated through application to the Mie potential, resulting in a thermodynamically consistent model seamlessly bridging fluid and crystalline phases. The proposed EoS accurately predicts metastable regions, enabling a comprehensive characterization of the phase diagram, which includes the critical and triple points. The article presents an equation of state (EoS) for fluid and solid phases using artificial neural networks. This EoS accurately models thermophysical properties and predicts phase transitions, including the critical and triple points. This approach offers a unified way to understand different states of matter.
{"title":"Development of a Helmholtz free energy equation of state for fluid and solid phases via artificial neural networks","authors":"Gustavo Chaparro, Erich A. Müller","doi":"10.1038/s42005-024-01892-3","DOIUrl":"10.1038/s42005-024-01892-3","url":null,"abstract":"A longstanding challenge in thermodynamics has been the development of a unified analytical expression for the free energy of matter capable of describing all thermodynamic properties. Although significant strides have been made in modeling fluid phases using continuous equations of state (EoSs), the crystalline state has remained largely unexplored because of its complexity. This work introduces an approach that employs artificial neural networks to construct an EoS directly from comprehensive molecular simulation data. The efficacy of this method is demonstrated through application to the Mie potential, resulting in a thermodynamically consistent model seamlessly bridging fluid and crystalline phases. The proposed EoS accurately predicts metastable regions, enabling a comprehensive characterization of the phase diagram, which includes the critical and triple points. The article presents an equation of state (EoS) for fluid and solid phases using artificial neural networks. This EoS accurately models thermophysical properties and predicts phase transitions, including the critical and triple points. This approach offers a unified way to understand different states of matter.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01892-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Mixing the fundamental (ω) and the second harmonic (2ω) waves in the gas phase is a widely employed technique for emitting terahertz (THz) pulses. The THz generation driven by bi-chromatic fields can be described by the photocurrent model, where the THz generation is attributed to free electrons ionized by the ω field, and the 2ω field provides a perturbation to break the symmetry of the asymptotic momentum of free electrons. However, we find that the THz radiation is amplified by one order of magnitude when driven by bi-focal bi-chromatic fields, which cannot be explained only using the photocurrent model. Meanwhile, present measurements demonstrate that the THz radiation mainly originates from the plasma created by the 2ω pulses instead of the ω pulses. Energy transfer from the 2ω beam to the THz beam during the THz generation has been observed, validating the major contribution of the 2ω beam. Furthermore, the THz bandwidth has been observed to extensively exceed the bandwidth of the pump pulse, not be explained by the photocurrent model as well. These counterintuitive results present a significant challenge for understanding strong-field nonlinear optics and simultaneously expanding various applications. Mixing the fundamental (ω) and the second harmonic (2ω) waves in the gas phase is a widely used technique for generating terahertz pulses. The authors experimentally present an enhanced terahertz emission through the temporal-spatial manipulation of bi-focal bi-chromatic fields, and the THz radiation mainly originates from the plasma created by the 2ω pulses instead of the ω pulses, which cannot be explained only using photocurrent model.
{"title":"Temporal-spatial manipulation of bi-focal bi-chromatic fields for terahertz radiations","authors":"Jingjing Zhao, Yizhu Zhang, Yanjun Gao, Meng Li, Xiaokun Liu, Weimin Liu, Tian-Min Yan, Yuhai Jiang","doi":"10.1038/s42005-024-01893-2","DOIUrl":"10.1038/s42005-024-01893-2","url":null,"abstract":"Mixing the fundamental (ω) and the second harmonic (2ω) waves in the gas phase is a widely employed technique for emitting terahertz (THz) pulses. The THz generation driven by bi-chromatic fields can be described by the photocurrent model, where the THz generation is attributed to free electrons ionized by the ω field, and the 2ω field provides a perturbation to break the symmetry of the asymptotic momentum of free electrons. However, we find that the THz radiation is amplified by one order of magnitude when driven by bi-focal bi-chromatic fields, which cannot be explained only using the photocurrent model. Meanwhile, present measurements demonstrate that the THz radiation mainly originates from the plasma created by the 2ω pulses instead of the ω pulses. Energy transfer from the 2ω beam to the THz beam during the THz generation has been observed, validating the major contribution of the 2ω beam. Furthermore, the THz bandwidth has been observed to extensively exceed the bandwidth of the pump pulse, not be explained by the photocurrent model as well. These counterintuitive results present a significant challenge for understanding strong-field nonlinear optics and simultaneously expanding various applications. Mixing the fundamental (ω) and the second harmonic (2ω) waves in the gas phase is a widely used technique for generating terahertz pulses. The authors experimentally present an enhanced terahertz emission through the temporal-spatial manipulation of bi-focal bi-chromatic fields, and the THz radiation mainly originates from the plasma created by the 2ω pulses instead of the ω pulses, which cannot be explained only using photocurrent model.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-6"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01893-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-19DOI: 10.1038/s42005-024-01875-4
Daniele Notarmuzi, Emanuela Bianchi
Despite the intrinsic charge heterogeneity of proteins plays a crucial role in the liquid-liquid phase separation (LLPS) of a broad variety of protein systems, our understanding of the effects of their electrostatic anisotropy is still in its early stages. We approach this issue by means of a coarse-grained model based on a robust mean-field description that extends the DLVO theory to non-uniformly charged particles. We numerically investigate the effect of surface charge patchiness and net particle charge on varying these features independently and with the use of a few parameters only. The effect of charge anisotropy on the LLPS critical point is rationalized via a thermodynamic-independent parameter based on orientationally averaged pair properties, that estimates the particle connectivity and controls the propensity of the liquid phase to condensate. We show that, even though directional attraction alone is able to lower the particle bonding valence—thus shifting the critical point towards lower temperatures and densities—directional repulsion significantly and systematically diminishes the particle functionality, thus further reducing the critical parameters. This electrostatically-driven shift can be understood in terms of the additional morphological constraints introduced by the directional repulsion, that hinder the condensation of dense aggregates. Experiments show that charge heterogeneity in proteins affects their liquid-liquid phase separation (LLPS). Using a theoretically grounded and numerically efficient coarse-grained model, the authors study how the amount of charge and its surface distribution affects the LLPS. They find that electrostatics controls the connectivity of particles thus impacting the emergence of the LLPS.
{"title":"Liquid-liquid phase separation driven by charge heterogeneity","authors":"Daniele Notarmuzi, Emanuela Bianchi","doi":"10.1038/s42005-024-01875-4","DOIUrl":"10.1038/s42005-024-01875-4","url":null,"abstract":"Despite the intrinsic charge heterogeneity of proteins plays a crucial role in the liquid-liquid phase separation (LLPS) of a broad variety of protein systems, our understanding of the effects of their electrostatic anisotropy is still in its early stages. We approach this issue by means of a coarse-grained model based on a robust mean-field description that extends the DLVO theory to non-uniformly charged particles. We numerically investigate the effect of surface charge patchiness and net particle charge on varying these features independently and with the use of a few parameters only. The effect of charge anisotropy on the LLPS critical point is rationalized via a thermodynamic-independent parameter based on orientationally averaged pair properties, that estimates the particle connectivity and controls the propensity of the liquid phase to condensate. We show that, even though directional attraction alone is able to lower the particle bonding valence—thus shifting the critical point towards lower temperatures and densities—directional repulsion significantly and systematically diminishes the particle functionality, thus further reducing the critical parameters. This electrostatically-driven shift can be understood in terms of the additional morphological constraints introduced by the directional repulsion, that hinder the condensation of dense aggregates. Experiments show that charge heterogeneity in proteins affects their liquid-liquid phase separation (LLPS). Using a theoretically grounded and numerically efficient coarse-grained model, the authors study how the amount of charge and its surface distribution affects the LLPS. They find that electrostatics controls the connectivity of particles thus impacting the emergence of the LLPS.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01875-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-19DOI: 10.1038/s42005-024-01894-1
Yuan-Mei Xie, Yu-Shuo Lu, Yao Fu, Hua-Lei Yin, Zeng-Bing Chen
Quantum conferencing enables multiple nodes within a quantum network to share a secure conference key for private message broadcasting. The key rate, however, is limited by the repeaterless capacity to distribute multipartite entangled states across the network. Currently, in the finite-size regime, no feasible schemes utilizing existing experimental techniques can overcome the fundamental rate-distance limit of quantum conferencing in quantum networks without repeaters. Here, we propose a practical, multi-field scheme that breaks this limit, involving virtually establishing Greenberger-Horne-Zeilinger states through post-measurement coincidence matching. This proposal features a measurement-device-independent characteristic and can directly scale to support any number of users. Simulations show that the fundamental limitation on the conference key rate can be overcome in a reasonable running time of sending 1014 pulses. We predict that it offers an efficient design for long-distance broadcast communication in future quantum networks. Quantum networks require secure conference keys for users to communicate and decrypt broadcasts. The authors propose a quantum conferencing protocol that overcomes key rate limits in networks without repeaters by using post-measurement coincidence matching, enabling secure, efficient, and flexible communication resistant to detector side channel attacks.
{"title":"Multi-field quantum conferencing overcomes the network capacity limit","authors":"Yuan-Mei Xie, Yu-Shuo Lu, Yao Fu, Hua-Lei Yin, Zeng-Bing Chen","doi":"10.1038/s42005-024-01894-1","DOIUrl":"10.1038/s42005-024-01894-1","url":null,"abstract":"Quantum conferencing enables multiple nodes within a quantum network to share a secure conference key for private message broadcasting. The key rate, however, is limited by the repeaterless capacity to distribute multipartite entangled states across the network. Currently, in the finite-size regime, no feasible schemes utilizing existing experimental techniques can overcome the fundamental rate-distance limit of quantum conferencing in quantum networks without repeaters. Here, we propose a practical, multi-field scheme that breaks this limit, involving virtually establishing Greenberger-Horne-Zeilinger states through post-measurement coincidence matching. This proposal features a measurement-device-independent characteristic and can directly scale to support any number of users. Simulations show that the fundamental limitation on the conference key rate can be overcome in a reasonable running time of sending 1014 pulses. We predict that it offers an efficient design for long-distance broadcast communication in future quantum networks. Quantum networks require secure conference keys for users to communicate and decrypt broadcasts. The authors propose a quantum conferencing protocol that overcomes key rate limits in networks without repeaters by using post-measurement coincidence matching, enabling secure, efficient, and flexible communication resistant to detector side channel attacks.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01894-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
In recent years, several proposals that leverage principles from condensed matter and high-energy physics for engineering laser arrays have been put forward. The most important among these concepts are topology, which enables the construction of robust zero-mode laser devices, and supersymmetry (SUSY), which holds the potential for achieving phase locking in laser arrays. In this work, we show that the relation between supersymmetric coupled bosonic and fermionic oscillators on one side, and bipartite networks (and hence chiral symmetry) on another side can be exploited together with non-Hermitian engineering for building one- and two-dimensional laser arrays with in-phase synchronization. To demonstrate our strategy, we present a concrete design starting from the celebrated Su-Schrieffer-Heeger (SSH) model to arrive at a SUSY laser structure that enjoys two key advantages over those reported in previous works. Firstly, the design presented here features a near-uniform geometry for both the laser array and supersymmetric reservoir (i.e., the widths and distances between the cavity arrays are almost the same). Secondly, the uniform field distribution in the presented structure leads to a far-field intensity that scales as N2 where N is the number of lasing elements. Taken together, these two features can enable the implementation of higher-power laser arrays that are easy to fabricate, and hence provide a roadmap for pushing the frontier of SUSY laser arrays beyond the proof-of-concept phase. In-phase synchronization of laser arrays remains one of the most important open problems in laser science. This work utilizes the relationship between chiral symmetric tight-binding models and supersymmetry to engineer a near-uniform laser array with a superior far-field intensity scaling, extending the frontiers of laser technology.
{"title":"A topological route to engineering robust and bright supersymmetric laser arrays","authors":"Soujanya Datta, Mohammadmahdi Alizadeh, Ramy El-Ganainy, Krishanu Roychowdhury","doi":"10.1038/s42005-024-01905-1","DOIUrl":"10.1038/s42005-024-01905-1","url":null,"abstract":"In recent years, several proposals that leverage principles from condensed matter and high-energy physics for engineering laser arrays have been put forward. The most important among these concepts are topology, which enables the construction of robust zero-mode laser devices, and supersymmetry (SUSY), which holds the potential for achieving phase locking in laser arrays. In this work, we show that the relation between supersymmetric coupled bosonic and fermionic oscillators on one side, and bipartite networks (and hence chiral symmetry) on another side can be exploited together with non-Hermitian engineering for building one- and two-dimensional laser arrays with in-phase synchronization. To demonstrate our strategy, we present a concrete design starting from the celebrated Su-Schrieffer-Heeger (SSH) model to arrive at a SUSY laser structure that enjoys two key advantages over those reported in previous works. Firstly, the design presented here features a near-uniform geometry for both the laser array and supersymmetric reservoir (i.e., the widths and distances between the cavity arrays are almost the same). Secondly, the uniform field distribution in the presented structure leads to a far-field intensity that scales as N2 where N is the number of lasing elements. Taken together, these two features can enable the implementation of higher-power laser arrays that are easy to fabricate, and hence provide a roadmap for pushing the frontier of SUSY laser arrays beyond the proof-of-concept phase. In-phase synchronization of laser arrays remains one of the most important open problems in laser science. This work utilizes the relationship between chiral symmetric tight-binding models and supersymmetry to engineer a near-uniform laser array with a superior far-field intensity scaling, extending the frontiers of laser technology.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01905-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
High harmonic generation (HHG) in solid-state materials is an emerging field of photonics research that can unveil the detailed electronic structure of materials, bond strengths and scattering processes of electrons. Although HHG in semiconducting and insulating materials has been intensively investigated both experimentally and theoretically, metals have rarely been explored because the strong screening effect of high-density free electrons is considered to significantly weaken the HHG signal. Here, we investigated HHG upon infrared excitation in bulk hexagonal metal titanium (Ti), a typical building block for practical lightweight structural materials. By analyzing the polarization dependence, the approach revealed the three-dimensional (3D) anisotropy in the electronic states. The results demonstrated the potential of HHG spectroscopy for characterizing 3D bonding anisotropy in metallic systems that are of fundamental importance for designing lightweight and strong structural materials. High harmonics generation (HHG) is a promising way of investigating electronic structures and anisotropy in materials. The authors demonstrate the observation of HHG in simple structural material, hexagonal metal titanium, and experimentally clarified the anisotropy in the electronic states from the polarization dependence.
{"title":"Three-dimensional bonding anisotropy of bulk hexagonal metal titanium demonstrated by high harmonic generation","authors":"Ikufumi Katayama, Kento Uchida, Kimika Takashina, Akari Kishioka, Misa Kaiho, Satoshi Kusaba, Ryo Tamaki, Ken-ichi Shudo, Masahiro Kitajima, Thien Duc Ngo, Tadaaki Nagao, Jun Takeda, Koichiro Tanaka, Tetsuya Matsunaga","doi":"10.1038/s42005-024-01906-0","DOIUrl":"10.1038/s42005-024-01906-0","url":null,"abstract":"High harmonic generation (HHG) in solid-state materials is an emerging field of photonics research that can unveil the detailed electronic structure of materials, bond strengths and scattering processes of electrons. Although HHG in semiconducting and insulating materials has been intensively investigated both experimentally and theoretically, metals have rarely been explored because the strong screening effect of high-density free electrons is considered to significantly weaken the HHG signal. Here, we investigated HHG upon infrared excitation in bulk hexagonal metal titanium (Ti), a typical building block for practical lightweight structural materials. By analyzing the polarization dependence, the approach revealed the three-dimensional (3D) anisotropy in the electronic states. The results demonstrated the potential of HHG spectroscopy for characterizing 3D bonding anisotropy in metallic systems that are of fundamental importance for designing lightweight and strong structural materials. High harmonics generation (HHG) is a promising way of investigating electronic structures and anisotropy in materials. The authors demonstrate the observation of HHG in simple structural material, hexagonal metal titanium, and experimentally clarified the anisotropy in the electronic states from the polarization dependence.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-7"},"PeriodicalIF":5.4,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01906-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-18DOI: 10.1038/s42005-024-01900-6
Danilo Enoque Ferreira de Lima, Arman Davtyan, Joakim Laksman, Natalia Gerasimova, Theophilos Maltezopoulos, Jia Liu, Philipp Schmidt, Thomas Michelat, Tommaso Mazza, Michael Meyer, Jan Grünert, Luca Gelisio
A reliable characterization of x-ray pulses is critical to optimally exploit advanced photon sources, such as free-electron lasers. In this paper, we present a method based on machine learning, the virtual spectrometer, that improves the resolution of non-invasive spectral diagnostics at the European XFEL by up to 40%, and significantly increases its signal-to-noise ratio. This improves the reliability of quasi-real-time monitoring, which is critical to steer the experiment, as well as the interpretation of experimental outcomes. Furthermore, the virtual spectrometer streamlines and automates the calibration of the spectral diagnostic device, which is otherwise a complex and time-consuming task, by virtue of its underlying detection principles. Additionally, the provision of robust quality metrics and uncertainties enable a transparent and reliable validation of the tool during its operation. A complete characterization of the virtual spectrometer under a diverse set of experimental and simulated conditions is provided in the manuscript, detailing advantages and limits, as well as its robustness with respect to the different test cases. A reliable characterization of x-ray pulses is critical to optimally exploit advanced photon sources, such as free-electron lasers. The authors present a method based on machine learning which improves the resolution and signal-to-noise ratio of the non-invasive spectral diagnostics available at European XFEL, and streamlines its operation.
{"title":"Machine-learning-enhanced automatic spectral characterization of x-ray pulses from a free-electron laser","authors":"Danilo Enoque Ferreira de Lima, Arman Davtyan, Joakim Laksman, Natalia Gerasimova, Theophilos Maltezopoulos, Jia Liu, Philipp Schmidt, Thomas Michelat, Tommaso Mazza, Michael Meyer, Jan Grünert, Luca Gelisio","doi":"10.1038/s42005-024-01900-6","DOIUrl":"10.1038/s42005-024-01900-6","url":null,"abstract":"A reliable characterization of x-ray pulses is critical to optimally exploit advanced photon sources, such as free-electron lasers. In this paper, we present a method based on machine learning, the virtual spectrometer, that improves the resolution of non-invasive spectral diagnostics at the European XFEL by up to 40%, and significantly increases its signal-to-noise ratio. This improves the reliability of quasi-real-time monitoring, which is critical to steer the experiment, as well as the interpretation of experimental outcomes. Furthermore, the virtual spectrometer streamlines and automates the calibration of the spectral diagnostic device, which is otherwise a complex and time-consuming task, by virtue of its underlying detection principles. Additionally, the provision of robust quality metrics and uncertainties enable a transparent and reliable validation of the tool during its operation. A complete characterization of the virtual spectrometer under a diverse set of experimental and simulated conditions is provided in the manuscript, detailing advantages and limits, as well as its robustness with respect to the different test cases. A reliable characterization of x-ray pulses is critical to optimally exploit advanced photon sources, such as free-electron lasers. The authors present a method based on machine learning which improves the resolution and signal-to-noise ratio of the non-invasive spectral diagnostics available at European XFEL, and streamlines its operation.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01900-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pub Date : 2024-12-18DOI: 10.1038/s42005-024-01880-7
Said Ouala, Bertrand Chapron, Fabrice Collard, Lucile Gaultier, Ronan Fablet
Defining end-to-end (or online) training schemes for the calibration of neural sub-models in hybrid systems requires working with an optimization problem that involves the solver of the physical equations. Online learning methodologies thus require the numerical model to be differentiable, which is not the case for most modeling systems. To overcome this, we present an efficient and practical online learning approach for hybrid systems. The method, called EGA for Euler Gradient Approximation, assumes an additive neural correction to the physical model, and an explicit Euler approximation of the gradients. We demonstrate that the EGA converges to the exact gradients in the limit of infinitely small time steps. Numerical experiments show significant improvements over offline learning, highlighting the potential of end-to-end learning for hybrid modeling. End-to-end learning in hybrid numerical models involves solving an optimization problem that integrates the model’s solver. In many fields, these solvers are written in low-abstraction programming languages that lack automatic differentiation. This work presents a practical approach to solving the optimization problem by efficiently approximating the gradient of the end-to-end objective function.
{"title":"Online calibration of deep learning sub-models for hybrid numerical modeling systems","authors":"Said Ouala, Bertrand Chapron, Fabrice Collard, Lucile Gaultier, Ronan Fablet","doi":"10.1038/s42005-024-01880-7","DOIUrl":"10.1038/s42005-024-01880-7","url":null,"abstract":"Defining end-to-end (or online) training schemes for the calibration of neural sub-models in hybrid systems requires working with an optimization problem that involves the solver of the physical equations. Online learning methodologies thus require the numerical model to be differentiable, which is not the case for most modeling systems. To overcome this, we present an efficient and practical online learning approach for hybrid systems. The method, called EGA for Euler Gradient Approximation, assumes an additive neural correction to the physical model, and an explicit Euler approximation of the gradients. We demonstrate that the EGA converges to the exact gradients in the limit of infinitely small time steps. Numerical experiments show significant improvements over offline learning, highlighting the potential of end-to-end learning for hybrid modeling. End-to-end learning in hybrid numerical models involves solving an optimization problem that integrates the model’s solver. In many fields, these solvers are written in low-abstraction programming languages that lack automatic differentiation. This work presents a practical approach to solving the optimization problem by efficiently approximating the gradient of the end-to-end objective function.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-15"},"PeriodicalIF":5.4,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01880-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
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