Pub Date : 2024-11-29DOI: 10.1038/s42005-024-01873-6
Zeyu Ma, Danrui Ni, David A. S. Kaib, Kylie MacFarquharson, John S. Pearce, Robert J. Cava, Roser Valentí, Radu Coldea, Amalia I. Coldea
In the Kitaev honeycomb model, spins coupled by strongly-frustrated anisotropic interactions do not order at low temperature but instead form a quantum spin liquid with spin fractionalisation into Majorana fermions and static fluxes. The realization of such a model in crystalline materials could lead to major breakthroughs in understanding entangled quantum states, however achieving this in practice is a very challenging task. The recently synthesized honeycomb material RuI3 shows no long-range magnetic order down to the lowest probed temperatures and has been theoretically proposed as a quantum spin liquid candidate material on the verge of an insulator to metal transition. Here we report a comprehensive study of the magnetic anisotropy in un-twinned single crystals via torque magnetometry and detect clear signatures of strongly anisotropic and frustrated magnetic interactions. We attribute the development of sawtooth and six-fold torque signal to strongly anisotropic, bond-dependent magnetic interactions by comparing to theoretical calculations. As a function of magnetic field strength at low temperatures, torque shows an unusual non-parabolic dependence suggestive of a proximity to a field-induced transition. Thus, RuI3, without signatures of long-range magnetic order, displays key hallmarks of an exciting candidate for extended Kitaev magnetism with enhanced quantum fluctuations. Quantum spin liquids are materials predicted to be absent of magnetic ordering at low temperature, giving rise to fractionalised electronic states, but conclusive experimental evidence is still absent. Here, the authors conduct angular dependent torque measurements on the candidate spin liquid material RuI3 and, through a comparison of experimental and theoretical results, provide evidence indicating the presence of frustrated magnetic interactions in the system.
{"title":"Anisotropic magnetic interactions in a candidate Kitaev spin liquid close to a metal-insulator transition","authors":"Zeyu Ma, Danrui Ni, David A. S. Kaib, Kylie MacFarquharson, John S. Pearce, Robert J. Cava, Roser Valentí, Radu Coldea, Amalia I. Coldea","doi":"10.1038/s42005-024-01873-6","DOIUrl":"10.1038/s42005-024-01873-6","url":null,"abstract":"In the Kitaev honeycomb model, spins coupled by strongly-frustrated anisotropic interactions do not order at low temperature but instead form a quantum spin liquid with spin fractionalisation into Majorana fermions and static fluxes. The realization of such a model in crystalline materials could lead to major breakthroughs in understanding entangled quantum states, however achieving this in practice is a very challenging task. The recently synthesized honeycomb material RuI3 shows no long-range magnetic order down to the lowest probed temperatures and has been theoretically proposed as a quantum spin liquid candidate material on the verge of an insulator to metal transition. Here we report a comprehensive study of the magnetic anisotropy in un-twinned single crystals via torque magnetometry and detect clear signatures of strongly anisotropic and frustrated magnetic interactions. We attribute the development of sawtooth and six-fold torque signal to strongly anisotropic, bond-dependent magnetic interactions by comparing to theoretical calculations. As a function of magnetic field strength at low temperatures, torque shows an unusual non-parabolic dependence suggestive of a proximity to a field-induced transition. Thus, RuI3, without signatures of long-range magnetic order, displays key hallmarks of an exciting candidate for extended Kitaev magnetism with enhanced quantum fluctuations. Quantum spin liquids are materials predicted to be absent of magnetic ordering at low temperature, giving rise to fractionalised electronic states, but conclusive experimental evidence is still absent. Here, the authors conduct angular dependent torque measurements on the candidate spin liquid material RuI3 and, through a comparison of experimental and theoretical results, provide evidence indicating the presence of frustrated magnetic interactions in the system.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01873-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758097","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 : 2024-11-28DOI: 10.1038/s42005-024-01876-3
Hannah C. Nerl, Khairi Elyas, Zdravko Kochovski, Nahid Talebi, Christoph T. Koch, Katja Höflich
Excitons are quasiparticles, comprised of an electron excited from the valence band and attracted to the hole left behind, that govern transport properties in transition metal dichalcogenides. Excitonic coherence specifically needs to be understood to realise applications based on Bose-Einstein condensation and superfluidity. Here we used momentum-resolved electron energy-loss spectroscopy to obtain the complete energy-momentum dispersion of excitons in thin film and monolayer WSe2 across the entire Brillouin zone, including outside of the light cone and for a large energy-loss range (1.5–4 eV). The measured dispersion of the modes was found to be flat. This suggests that the excitations are at the onset of polaritonic mode formation, propagating in the confinement of nanometer thin and monolayer WSe2. In combination with helium ion microscopy nanopatterning it was possible to probe and control these excitonic modes in thin film WSe2 by modifying the local geometry through nanosized cuts. The coupling of an exciton to an electromagnetic field leads to the formation of an exciton polariton and in transition metal dichalcogenides specifically, they might be candidates for room temperature Bose-Einstein condensation. Here, the authors observe excitons at the onset of polaritonic mode formation in the confinement of nanometer thin and monolayer WSe2. Excitonic intensities were controlled locally by nanosized modifications to the material’s geometry.
{"title":"Flat dispersion at large momentum transfer at the onset of exciton polariton formation","authors":"Hannah C. Nerl, Khairi Elyas, Zdravko Kochovski, Nahid Talebi, Christoph T. Koch, Katja Höflich","doi":"10.1038/s42005-024-01876-3","DOIUrl":"10.1038/s42005-024-01876-3","url":null,"abstract":"Excitons are quasiparticles, comprised of an electron excited from the valence band and attracted to the hole left behind, that govern transport properties in transition metal dichalcogenides. Excitonic coherence specifically needs to be understood to realise applications based on Bose-Einstein condensation and superfluidity. Here we used momentum-resolved electron energy-loss spectroscopy to obtain the complete energy-momentum dispersion of excitons in thin film and monolayer WSe2 across the entire Brillouin zone, including outside of the light cone and for a large energy-loss range (1.5–4 eV). The measured dispersion of the modes was found to be flat. This suggests that the excitations are at the onset of polaritonic mode formation, propagating in the confinement of nanometer thin and monolayer WSe2. In combination with helium ion microscopy nanopatterning it was possible to probe and control these excitonic modes in thin film WSe2 by modifying the local geometry through nanosized cuts. The coupling of an exciton to an electromagnetic field leads to the formation of an exciton polariton and in transition metal dichalcogenides specifically, they might be candidates for room temperature Bose-Einstein condensation. Here, the authors observe excitons at the onset of polaritonic mode formation in the confinement of nanometer thin and monolayer WSe2. Excitonic intensities were controlled locally by nanosized modifications to the material’s geometry.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01876-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758086","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 : 2024-11-28DOI: 10.1038/s42005-024-01879-0
C. J. Sayers, Y. Zhang, C. E. Sanders, R. T. Chapman, A. S. Wyatt, G. Chatterjee, E. Springate, G. Cerullo, D. Wolverson, E. Da Como, E. Carpene
The driving force of a charge density wave (CDW) transition in quasi-two dimensional systems is still debated, while being crucial in understanding electronic correlation in such materials. Here we use femtosecond time- and angle-resolved photoemission spectroscopy combined with computational methods to investigate the coherent lattice dynamics of a prototypical CDW system. The photo-induced temporal evolution of the periodic lattice distortion associated with the amplitude mode reveals the dynamics of the free energy functional governing the order parameter. Our approach establishes that optically-induced screening rather than CDW melting at the electronic level leads to a transiently modified potential which explains the anharmonic behaviour of the amplitude mode and discloses the structural origin of the symmetry-breaking phase transition. The charge density wave (CDW) formation mechanisms in 2D and quasi-2D systems are still highly debated. Here, the authors combine time-resolved ARPES and ab initio calculations to map the free energy functional in the prototypical CDW compound 1T-TaSe2 concluding that the CDW state is driven by structural rather than electronic instabilities.
{"title":"Mapping the nonequilibrium order parameter of a quasi-two dimensional charge density wave system","authors":"C. J. Sayers, Y. Zhang, C. E. Sanders, R. T. Chapman, A. S. Wyatt, G. Chatterjee, E. Springate, G. Cerullo, D. Wolverson, E. Da Como, E. Carpene","doi":"10.1038/s42005-024-01879-0","DOIUrl":"10.1038/s42005-024-01879-0","url":null,"abstract":"The driving force of a charge density wave (CDW) transition in quasi-two dimensional systems is still debated, while being crucial in understanding electronic correlation in such materials. Here we use femtosecond time- and angle-resolved photoemission spectroscopy combined with computational methods to investigate the coherent lattice dynamics of a prototypical CDW system. The photo-induced temporal evolution of the periodic lattice distortion associated with the amplitude mode reveals the dynamics of the free energy functional governing the order parameter. Our approach establishes that optically-induced screening rather than CDW melting at the electronic level leads to a transiently modified potential which explains the anharmonic behaviour of the amplitude mode and discloses the structural origin of the symmetry-breaking phase transition. The charge density wave (CDW) formation mechanisms in 2D and quasi-2D systems are still highly debated. Here, the authors combine time-resolved ARPES and ab initio calculations to map the free energy functional in the prototypical CDW compound 1T-TaSe2 concluding that the CDW state is driven by structural rather than electronic instabilities.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-6"},"PeriodicalIF":5.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01879-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758123","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 : 2024-11-28DOI: 10.1038/s42005-024-01883-4
Samuel C. Smith, Benjamin J. Brown, Stephen D. Bartlett
Quantum error correcting codes can enable large quantum computations provided physical error rates are sufficiently low. We combine post-selection with surface code error correction through the use of exclusive decoders, which abort on decoding instances that are deemed too difficult. For the most discriminating of exclusive decoders, we demonstrate a threshold of 50% under depolarizing noise (or 32(1)% for the fault-tolerant case), and up to a quadratic improvement in logical failure rates below threshold. Furthermore, with a modest exclusion criterion, we identify a regime at low error rates where the exclusion rate decays with code distance, providing a pathway for scalable and time-efficient quantum computing with post-selection. Our exclusive decoder applied to magic state distillation yields a 75% reduction in the number of physical qubits, and a 60% reduction in the total spacetime volume, including accounting for repetitions. Other applications include error mitigation, and in concatenated schemes. Quantum error correction produces an enormous amount of data about the quantum system, including information about whether an uncorrectable error is likely. In this work the authors analyse a new decoder that can abort when decoding is deemed too difficult, yielding improved performance overall.
{"title":"Mitigating errors in logical qubits","authors":"Samuel C. Smith, Benjamin J. Brown, Stephen D. Bartlett","doi":"10.1038/s42005-024-01883-4","DOIUrl":"10.1038/s42005-024-01883-4","url":null,"abstract":"Quantum error correcting codes can enable large quantum computations provided physical error rates are sufficiently low. We combine post-selection with surface code error correction through the use of exclusive decoders, which abort on decoding instances that are deemed too difficult. For the most discriminating of exclusive decoders, we demonstrate a threshold of 50% under depolarizing noise (or 32(1)% for the fault-tolerant case), and up to a quadratic improvement in logical failure rates below threshold. Furthermore, with a modest exclusion criterion, we identify a regime at low error rates where the exclusion rate decays with code distance, providing a pathway for scalable and time-efficient quantum computing with post-selection. Our exclusive decoder applied to magic state distillation yields a 75% reduction in the number of physical qubits, and a 60% reduction in the total spacetime volume, including accounting for repetitions. Other applications include error mitigation, and in concatenated schemes. Quantum error correction produces an enormous amount of data about the quantum system, including information about whether an uncorrectable error is likely. In this work the authors analyse a new decoder that can abort when decoding is deemed too difficult, yielding improved performance overall.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-10"},"PeriodicalIF":5.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01883-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758127","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 : 2024-11-28DOI: 10.1038/s42005-024-01886-1
A. M. Marques, D. Viedma, V. Ahufinger, R. G. Dias
Flat band (FB) systems, featuring dispersionless energy bands, have garnered significant interest due to their compact localized states (CLSs). However, a detailed account on how local impurities affect the physical properties of overlapping CLSs is still missing. Here we study a diamond chain with a finite magnetic flux per plaquette that exhibits a gapped midspectrum FB with non-orthogonal CLSs, and develop a framework for projecting operators onto such non-orthogonal bases. This framework is applied to the case of an open diamond chain with small local impurities in the midchain plaquette, and analytical expressions are derived for FB states influenced by these impurities. For equal impurities in top and bottom sites under diagonal disorder, we show how the impurity states experience an averaged disorder dependent on their spatial extension, leading to enhanced robustness against disorder. For a single impurity, an exotic topological phase with a half-integer winding number is discovered, which is linked to a single in-gap edge state under open boundary conditions. Numerical simulations validate the analytical predictions. Flat bands states can be written, in general, as localized states that can couple by placing impurities at the overlapping regions, when present. The authors develop an analytic framework to derive impurity states in a diamond chain with magnetic flux and find an exotic behavior of these states characterized by a half-integer winding number.
{"title":"Impurity flat band states in the diamond chain","authors":"A. M. Marques, D. Viedma, V. Ahufinger, R. G. Dias","doi":"10.1038/s42005-024-01886-1","DOIUrl":"10.1038/s42005-024-01886-1","url":null,"abstract":"Flat band (FB) systems, featuring dispersionless energy bands, have garnered significant interest due to their compact localized states (CLSs). However, a detailed account on how local impurities affect the physical properties of overlapping CLSs is still missing. Here we study a diamond chain with a finite magnetic flux per plaquette that exhibits a gapped midspectrum FB with non-orthogonal CLSs, and develop a framework for projecting operators onto such non-orthogonal bases. This framework is applied to the case of an open diamond chain with small local impurities in the midchain plaquette, and analytical expressions are derived for FB states influenced by these impurities. For equal impurities in top and bottom sites under diagonal disorder, we show how the impurity states experience an averaged disorder dependent on their spatial extension, leading to enhanced robustness against disorder. For a single impurity, an exotic topological phase with a half-integer winding number is discovered, which is linked to a single in-gap edge state under open boundary conditions. Numerical simulations validate the analytical predictions. Flat bands states can be written, in general, as localized states that can couple by placing impurities at the overlapping regions, when present. The authors develop an analytic framework to derive impurity states in a diamond chain with magnetic flux and find an exotic behavior of these states characterized by a half-integer winding number.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-12"},"PeriodicalIF":5.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01886-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758129","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 : 2024-11-26DOI: 10.1038/s42005-024-01871-8
Aaveg Aggarwal, Shih-Yuan Chen, Eleftherios Kirkinis, Mohammed Imran Khan, Bei Fan, Michelle M. Driscoll, Monica Olvera de la Cruz
Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. Magnetic fields, in particular, carry the added advantage of biocompatibility as well as being able to actuate materials remotely. Although ferrofluid droplet migration induced by a high-frequency rotating magnetic field is a well-established effect, droplet migration at low frequencies is still elusive. Millimeter-sized ferrofluid droplets placed on a solid substrate, surrounded by an ambient gas phase, are shown here to migrate under a rotating magnetic field due to inertia-induced symmetry-breaking of the periodic deformation (wobbling) of the liquid-gas interface. This interface wobbling leads to droplet migration with speeds that increase as the amplitude and frequency of the magnetic field increase. In addition to migrating in a controlled manner, we demonstrate the ability of magnetic droplets to clean surface impurities and transport cargo. Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. In this study, the authors show that a rotating magnetic field leads a ferrofluid droplet to wobble, migrate, clean surface impurities and transport cargo.
{"title":"Wobbling and migrating ferrofluid droplets","authors":"Aaveg Aggarwal, Shih-Yuan Chen, Eleftherios Kirkinis, Mohammed Imran Khan, Bei Fan, Michelle M. Driscoll, Monica Olvera de la Cruz","doi":"10.1038/s42005-024-01871-8","DOIUrl":"10.1038/s42005-024-01871-8","url":null,"abstract":"Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. Magnetic fields, in particular, carry the added advantage of biocompatibility as well as being able to actuate materials remotely. Although ferrofluid droplet migration induced by a high-frequency rotating magnetic field is a well-established effect, droplet migration at low frequencies is still elusive. Millimeter-sized ferrofluid droplets placed on a solid substrate, surrounded by an ambient gas phase, are shown here to migrate under a rotating magnetic field due to inertia-induced symmetry-breaking of the periodic deformation (wobbling) of the liquid-gas interface. This interface wobbling leads to droplet migration with speeds that increase as the amplitude and frequency of the magnetic field increase. In addition to migrating in a controlled manner, we demonstrate the ability of magnetic droplets to clean surface impurities and transport cargo. Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. In this study, the authors show that a rotating magnetic field leads a ferrofluid droplet to wobble, migrate, clean surface impurities and transport cargo.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-7"},"PeriodicalIF":5.4,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01871-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714742","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 : 2024-11-26DOI: 10.1038/s42005-024-01868-3
Michael Klaiber, Karen Z. Hatsagortsyan, Christoph H. Keitel
The time delay in strong field tunneling ionization presents a captivating challenge in the field of attoscience. It is linked to the phase of the photoelectron wavepacket, a relationship that modern attosecond photoelectron interferometry can effectively probe. However, the connection between sub-barrier dynamics and the phase formation remains unclear. In this study, we investigate the role of under-the-barrier recollisions for shaping the phase of the photoelectron wavepacket. We establish a general analytical relationship between the phase of the tunneled electron wavepacket and the tunneling rate. Our results demonstrate that the Coulomb field effect of the atomic potential enhances both the amplitude of the recolliding path and the phase shift of the wavepacket, effectively countering the lateral spreading of the tunneling wavepacket during sub-barrier propagation. The insights gained from this research will aid in the development of free electron wavepackets with tailored properties through strong field ionization. This work investigates the origin of time delay in strong field tunneling ionization and its relation to the parameters of the photoelectron wavepacket. The authors establish a general analytical relationship between the phase of the wavepacket and the tunneling rate, and analyze the role of under-the-barrier recollisions for shaping the photoelectron wavepacket.
{"title":"Signatures of under-the-barrier dynamics in a tunneling electron wavepacket","authors":"Michael Klaiber, Karen Z. Hatsagortsyan, Christoph H. Keitel","doi":"10.1038/s42005-024-01868-3","DOIUrl":"10.1038/s42005-024-01868-3","url":null,"abstract":"The time delay in strong field tunneling ionization presents a captivating challenge in the field of attoscience. It is linked to the phase of the photoelectron wavepacket, a relationship that modern attosecond photoelectron interferometry can effectively probe. However, the connection between sub-barrier dynamics and the phase formation remains unclear. In this study, we investigate the role of under-the-barrier recollisions for shaping the phase of the photoelectron wavepacket. We establish a general analytical relationship between the phase of the tunneled electron wavepacket and the tunneling rate. Our results demonstrate that the Coulomb field effect of the atomic potential enhances both the amplitude of the recolliding path and the phase shift of the wavepacket, effectively countering the lateral spreading of the tunneling wavepacket during sub-barrier propagation. The insights gained from this research will aid in the development of free electron wavepackets with tailored properties through strong field ionization. This work investigates the origin of time delay in strong field tunneling ionization and its relation to the parameters of the photoelectron wavepacket. The authors establish a general analytical relationship between the phase of the wavepacket and the tunneling rate, and analyze the role of under-the-barrier recollisions for shaping the photoelectron wavepacket.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01868-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714735","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 : 2024-11-25DOI: 10.1038/s42005-024-01882-5
Pinxuan He, Jiamin Liu, Honggang Gu, Hao Jiang, Shiyuan Liu
Numerical electromagnetic field solvers are significant for nanophotonic and photoelectronic technology, especially for computational imaging, metasurface, and biomedical microscopy, in which large-scale simulations serve as the core. Conventionally, these simulations use absorbing boundary conditions (ABC) to simulate open-domain systems. However, the existing ABCs require large memory to sufficiently suppress reflection at boundaries, which is prohibitive for large-scale applications. This work proposes a virtual absorbing boundary condition based on the angular spectrum method (ASM) to reduce the memory usage of ABC. The ASM is used to cover the polluted field in the boundary region, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit. This proposed method offers a substantial boost for applications related to large-scale simulations and memory-constrained devices like GPU. This work proposes a virtual boundary condition based on the angular spectrum method to reduce memory usage in electromagnetic simulations, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit.
{"title":"Modified Born series with virtual absorbing boundary enabling large-scale electromagnetic simulation","authors":"Pinxuan He, Jiamin Liu, Honggang Gu, Hao Jiang, Shiyuan Liu","doi":"10.1038/s42005-024-01882-5","DOIUrl":"10.1038/s42005-024-01882-5","url":null,"abstract":"Numerical electromagnetic field solvers are significant for nanophotonic and photoelectronic technology, especially for computational imaging, metasurface, and biomedical microscopy, in which large-scale simulations serve as the core. Conventionally, these simulations use absorbing boundary conditions (ABC) to simulate open-domain systems. However, the existing ABCs require large memory to sufficiently suppress reflection at boundaries, which is prohibitive for large-scale applications. This work proposes a virtual absorbing boundary condition based on the angular spectrum method (ASM) to reduce the memory usage of ABC. The ASM is used to cover the polluted field in the boundary region, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit. This proposed method offers a substantial boost for applications related to large-scale simulations and memory-constrained devices like GPU. This work proposes a virtual boundary condition based on the angular spectrum method to reduce memory usage in electromagnetic simulations, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01882-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714748","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}
Quantifying the strain, and even the strain state, is critical for the advancement of strain engineering in microelectronics and optoelectronics fields, whether using the classical semiconductors or emerging two-dimensional materials. Second Harmonic Generation (SHG) has emerged as a potent technique for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides (2D-TMDCs). Based on the theoretical framework of SHG, this work analyses the mechanism of different strain states acting on the SHG polarization-intensity spectrum (PIS) of MoS2. A quantifying method is proposed by establishing the analytic relationship between the in-plane strain components and the petal amplitude ratios (PARs) obtained from detected PIS. After calibrating the key parameters of MoS2 SHG PIS, a series of biaxial and uniaxial tensile experiments are performed, whose results are mostly agreed with the theoretical expectations, thus verifying the reliability, correctness and universality of the proposed method for quantitively characterizing the strain state of monolayer MoS2. Second Harmonic Generation (SHG) is potent for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides. This work presents a method to quantify the strain state influence on the SHG polarization-intensity spectrum of MoS2, and the reliability of proposed method is verified by numerical and physical experiments.
{"title":"Quantifying the in-plane strain influence on second harmonic generation of molybdenum disulfide","authors":"Huadan Xing, Jibin Liu, Zihao Zhao, Xiaoyong He, Wei Qiu","doi":"10.1038/s42005-024-01877-2","DOIUrl":"10.1038/s42005-024-01877-2","url":null,"abstract":"Quantifying the strain, and even the strain state, is critical for the advancement of strain engineering in microelectronics and optoelectronics fields, whether using the classical semiconductors or emerging two-dimensional materials. Second Harmonic Generation (SHG) has emerged as a potent technique for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides (2D-TMDCs). Based on the theoretical framework of SHG, this work analyses the mechanism of different strain states acting on the SHG polarization-intensity spectrum (PIS) of MoS2. A quantifying method is proposed by establishing the analytic relationship between the in-plane strain components and the petal amplitude ratios (PARs) obtained from detected PIS. After calibrating the key parameters of MoS2 SHG PIS, a series of biaxial and uniaxial tensile experiments are performed, whose results are mostly agreed with the theoretical expectations, thus verifying the reliability, correctness and universality of the proposed method for quantitively characterizing the strain state of monolayer MoS2. Second Harmonic Generation (SHG) is potent for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides. This work presents a method to quantify the strain state influence on the SHG polarization-intensity spectrum of MoS2, and the reliability of proposed method is verified by numerical and physical experiments.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-10"},"PeriodicalIF":5.4,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01877-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714739","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 : 2024-11-22DOI: 10.1038/s42005-024-01869-2
Stefano Biasi, Alessio Lugnan, Davide Micheli, Lorenzo Pavesi
Photonic platforms are promising for implementing neuromorphic hardware due to their high processing speed, low power consumption, and ability to perform parallel processing. A ubiquitous device in integrated photonics, which has been extensively employed for the realization of optical neuromorphic hardware, is the microresonator. The ability of CMOS-compatible silicon microring resonators to store energy enhances the nonlinear interaction between light and matter, enabling energy efficient nonlinearity, fading memory and the generation of spikes via self-pulsing. In the self-pulsing regime, a constant input signal can be transformed into a time-dependent signal based on pulse sequences. Previous research has shown that self-pulsing enables the microresonator to function as an energy-efficient artificial spiking neuron. Here, we extend the experimental study of single and coupled microresonators in the self-pulsing regime to confirm their potential as building blocks for scalable photonic spiking neural networks. Furthermore, we demonstrate their potential for introducing all-optical long-term memory and event detection capabilities into integrated photonic neural networks. In particular, we show all-optical long-term memory up to at least 10 μs and detection of input spike rates, which is encoded into different stable self-pulsing dynamics. While silicon photonics is an attractive platform for neuromorphic computing, it generally lacks scalable nodes that provide nonlinearity and memory. Here, the authors show experimentally that simple and compact networks of silicon microring resonators exhibit complex self-pulsing responses that can be exploited for all-optical long-term memory and sensing.
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