Pub Date : 2024-06-30DOI: 10.1088/0256-307x/41/7/077402
Meng Wang, 猛 王, Hai-Hu Wen, 海虎 闻, Tao Wu, 涛 吴, Dao-Xin Yao, 道新 姚, Tao Xiang and 涛 向
This review provides a comprehensive overview of current research on the structural, electronic, and magnetic characteristics of the recently discovered high-temperature superconductor La3Ni2O7 under high pressures. We present the experimental results for synthesizing and characterizing this material, derived from measurements of transport, thermodynamics, and various spectroscopic techniques, and discuss their physical implications. We also explore theoretical models proposed to describe the electronic structures and superconducting pairing symmetry in La3Ni2O7, highlighting the intricate interplay between electronic correlations and magnetic interactions. Despite these advances, challenges remain in growing high-quality samples free of extrinsic phases and oxygen deficiencies and in developing reliable measurement tools for determining diamagnetism and other physical quantities under high pressures. Further investigations in these areas are essential to deepening our understanding of the physical properties of La3Ni2O7 and unlocking its superconducting pairing mechanism.
{"title":"Normal and Superconducting Properties of La3Ni2O7","authors":"Meng Wang, 猛 王, Hai-Hu Wen, 海虎 闻, Tao Wu, 涛 吴, Dao-Xin Yao, 道新 姚, Tao Xiang and 涛 向","doi":"10.1088/0256-307x/41/7/077402","DOIUrl":"https://doi.org/10.1088/0256-307x/41/7/077402","url":null,"abstract":"This review provides a comprehensive overview of current research on the structural, electronic, and magnetic characteristics of the recently discovered high-temperature superconductor La3Ni2O7 under high pressures. We present the experimental results for synthesizing and characterizing this material, derived from measurements of transport, thermodynamics, and various spectroscopic techniques, and discuss their physical implications. We also explore theoretical models proposed to describe the electronic structures and superconducting pairing symmetry in La3Ni2O7, highlighting the intricate interplay between electronic correlations and magnetic interactions. Despite these advances, challenges remain in growing high-quality samples free of extrinsic phases and oxygen deficiencies and in developing reliable measurement tools for determining diamagnetism and other physical quantities under high pressures. Further investigations in these areas are essential to deepening our understanding of the physical properties of La3Ni2O7 and unlocking its superconducting pairing mechanism.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"27 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141745954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-06-30DOI: 10.1088/0256-307x/41/7/070501
Yu Zhong, 毓 钟, Houria Triki, Qin Zhou and 勤 周
This work focuses on the evolution behaviors of ring dark solitons (RDSs) and the following vortices after the collapses of RDSs in spin-1 Bose–Einstein condensates. We find that the weighted average of the initial depths of three components determines the number and motion trajectories of vortex dipoles. For the weighted average of the initial depths below the critical depth, two vortex dipoles form and start moving along the horizontal axis. For the weighted average depth above the critical depth, two or four vortex dipoles form, and all start moving along the vertical axis. For the RDS with weighted average depth at exactly the critical point, four vortex dipoles form, half of the vortex dipoles initiate movement vertically, and the other half initiate movement horizontally. Our conclusion is applicable to the two-component system studied in earlier research, indicating its universality.
{"title":"Dynamics of Ring Dark Solitons and the Following Vortices in Spin-1 Bose–Einstein Condensates","authors":"Yu Zhong, 毓 钟, Houria Triki, Qin Zhou and 勤 周","doi":"10.1088/0256-307x/41/7/070501","DOIUrl":"https://doi.org/10.1088/0256-307x/41/7/070501","url":null,"abstract":"This work focuses on the evolution behaviors of ring dark solitons (RDSs) and the following vortices after the collapses of RDSs in spin-1 Bose–Einstein condensates. We find that the weighted average of the initial depths of three components determines the number and motion trajectories of vortex dipoles. For the weighted average of the initial depths below the critical depth, two vortex dipoles form and start moving along the horizontal axis. For the weighted average depth above the critical depth, two or four vortex dipoles form, and all start moving along the vertical axis. For the RDS with weighted average depth at exactly the critical point, four vortex dipoles form, half of the vortex dipoles initiate movement vertically, and the other half initiate movement horizontally. Our conclusion is applicable to the two-component system studied in earlier research, indicating its universality.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"35 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141884479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
The rattling mode, an anharmonic vibrational phonon, is widely recognized as a critical factor in the emergence of superconductivity in caged materials. Here, we present a counterexample in a filled-skutterudite superconductor BaxIr4Sb12 (x = 0.8, 0.9, 1.0), synthesized via a high-pressure route. Transport measurements down to liquid 3He temperatures reveal a transition temperature (Tc) of 1.2 K and an upper critical field (Hc2) of 1.3 T. Unlike other superconductors with caged structures, the BaxIr4X12 (X = P, As, Sb) family exhibits a monotonic decreasing Tc with the enhancement of the rattling mode, as indicated by fitting the Bloch–Grüneisen formula. Theoretical analysis suggests that electron doping from Ba transforms the direct bandgap IrSb3 into a metal, with the Fermi surface dominated by the hybridization of Ir 5d and Sb 5p orbitals. Our findings of decoupled rattling modes and superconductivity distinguish the BaxIr4Sb12 family from other caged superconductors, warranting further exploration into the underlying mechanism.
嘎嘎模式是一种非谐振声子，被广泛认为是笼型材料出现超导电性的关键因素。在这里，我们提出了一个反例，即通过高压途径合成的填充砚石超导体 BaxIr4Sb12（x = 0.8、0.9、1.0）。与其他具有笼状结构的超导体不同，BaxIr4X12（X = P、As、Sb）系列表现出随着响振模式的增强而单调递减的 Tc，这一点可以通过布洛赫-格吕尼森公式拟合得到。理论分析表明，来自 Ba 的电子掺杂将直接带隙 IrSb3 转变为金属，费米面由 Ir 5d 和 Sb 5p 轨道杂化主导。我们发现的解耦响声模式和超导性使 BaxIr4Sb12 系列有别于其他笼型超导体，值得进一步探索其基本机制。
{"title":"Decoupling of Rattling Mode and Superconductivity in Filled-Skutterudite BaxIr4Sb12","authors":"Hui Liu, 辉 刘, Tongxu Yu, 同旭 于, Zhihua Zhang, 志华 张, Tianping Ying and 天平 应","doi":"10.1088/0256-307x/41/7/077401","DOIUrl":"https://doi.org/10.1088/0256-307x/41/7/077401","url":null,"abstract":"The rattling mode, an anharmonic vibrational phonon, is widely recognized as a critical factor in the emergence of superconductivity in caged materials. Here, we present a counterexample in a filled-skutterudite superconductor BaxIr4Sb12 (x = 0.8, 0.9, 1.0), synthesized via a high-pressure route. Transport measurements down to liquid 3He temperatures reveal a transition temperature (Tc) of 1.2 K and an upper critical field (Hc2) of 1.3 T. Unlike other superconductors with caged structures, the BaxIr4X12 (X = P, As, Sb) family exhibits a monotonic decreasing Tc with the enhancement of the rattling mode, as indicated by fitting the Bloch–Grüneisen formula. Theoretical analysis suggests that electron doping from Ba transforms the direct bandgap IrSb3 into a metal, with the Fermi surface dominated by the hybridization of Ir 5d and Sb 5p orbitals. Our findings of decoupled rattling modes and superconductivity distinguish the BaxIr4Sb12 family from other caged superconductors, warranting further exploration into the underlying mechanism.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"342 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141753875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO2(B)] quantum material. It is shown that the initial metallic state in the VO2(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO2(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.
{"title":"Ultrasensitive Mechanical Sensor Using Tunable Ordered Array of Metallic and Insulating States in Vanadium Dioxide","authors":"Zecheng Ma, 泽成 马, Shengnan Yan, 胜楠 闫, Fanqiang Chen, 繁强 陈, Yudi Dai, 玉頔 戴, Zenglin Liu, 增霖 刘, Kang Xu, 康 徐, Tao Xu, 涛 徐, Zhanqin Tong, 湛钦 童, Moyu Chen, 墨雨 陈, Lizheng Wang, 利铮 王, Pengfei Wang, 鹏飞 王, Litao Sun, 立涛 孙, Bin Cheng, 斌 程, Shi-Jun Liang, 世军 梁, Feng Miao and 峰 缪","doi":"10.1088/0256-307x/41/7/077101","DOIUrl":"https://doi.org/10.1088/0256-307x/41/7/077101","url":null,"abstract":"Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO2(B)] quantum material. It is shown that the initial metallic state in the VO2(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO2(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"340 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
In the era of Internet of Things (IoTs), an energy-efficient ultraviolet (UV) photodetector (PD) is highly desirable considering the massive usage scenarios such as environmental sterilization, fire alarm and corona discharge monitoring. So far, common self-powered UV PDs are mainly based on metal-semiconductor hetero-structures or p–n heterojunctions, where the limited intrinsic built-in electric field restricts further enhancement of the photoresponsivity. In this work, an extremely low-voltage field-effect UV PD is proposed using a gate-drain shorted amorphous IGZO (a-IGZO) thin film transistor (TFT) architecture. A combined investigation of the experimental measurements and technology computer-aided design (TCAD) simulations suggests that the reverse current (IR) of field-effect diode (FED) is highly related with the threshold voltage (Vth) of the parental TFT, implying an enhancement-mode TFT is preferable to fabricate the field-effect UV PD with low dark current. Driven by a low bias of −0.1 V, decent UV response has been realized including large UV/visible (R300/R550) rejection ratio (1.9 × 103), low dark current (1.15 × 10−12 A) as well as high photo-to-dark current ratio (PDCR, ∼ 103) and responsivity (1.89 A/W). This field-effect photodiode provides a new platform to construct UV PDs with well-balanced photoresponse performance at a low bias, which is attractive for designs of large-scale smart sensor networks with high energy efficiency.
{"title":"Low-Voltage IGZO Field-Effect Ultraviolet Photodiode","authors":"Shuang Song, Huili Liang, Wenxing Huo, Guang Zhang, Yonghui Zhang, Jiwei Wang, Zengxia Mei","doi":"10.1088/0256-307x/41/6/068501","DOIUrl":"https://doi.org/10.1088/0256-307x/41/6/068501","url":null,"abstract":"In the era of Internet of Things (IoTs), an energy-efficient ultraviolet (UV) photodetector (PD) is highly desirable considering the massive usage scenarios such as environmental sterilization, fire alarm and corona discharge monitoring. So far, common self-powered UV PDs are mainly based on metal-semiconductor hetero-structures or p–n heterojunctions, where the limited intrinsic built-in electric field restricts further enhancement of the photoresponsivity. In this work, an extremely low-voltage field-effect UV PD is proposed using a gate-drain shorted amorphous IGZO (a-IGZO) thin film transistor (TFT) architecture. A combined investigation of the experimental measurements and technology computer-aided design (TCAD) simulations suggests that the reverse current (<italic toggle=\"yes\">I</italic><sub>R</sub>) of field-effect diode (FED) is highly related with the threshold voltage (<italic toggle=\"yes\">V</italic><sub>th</sub>) of the parental TFT, implying an enhancement-mode TFT is preferable to fabricate the field-effect UV PD with low dark current. Driven by a low bias of −0.1 V, decent UV response has been realized including large UV/visible (<italic toggle=\"yes\">R</italic><sub>300</sub>/<italic toggle=\"yes\">R</italic><sub>550</sub>) rejection ratio (1.9 × 10<sup>3</sup>), low dark current (1.15 × 10<sup>−12</sup> A) as well as high photo-to-dark current ratio (PDCR, ∼ 10<sup>3</sup>) and responsivity (1.89 A/W). This field-effect photodiode provides a new platform to construct UV PDs with well-balanced photoresponse performance at a low bias, which is attractive for designs of large-scale smart sensor networks with high energy efficiency.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"40 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-06-01DOI: 10.1088/1674-1056/ad43d4
Nan Bo, Nai-Yan Wang
Based on previously reported work, we propose a new method for calibrating image plate (IP) scanners, offering greater flexibility and convenience, which can be extended to the calibration tasks of various scanner models. This method was applied to calibrate the sensitivity of a GE Typhoon FLA 7000 scanner. Additionally, we performed a calibration of the spontaneous signal attenuation behavior for BAS-MS, BAS-SR, and BAS-TR type IPs under the 20±1 °C environmental conditions, and observed significant signal carrier diffusion behavior in BAS-MS IP. The calibration results lay a foundation for further research on the interaction between ultra-short, ultra-intense lasers and matter.
在之前报告工作的基础上，我们提出了一种校准图像平板（IP）扫描仪的新方法，该方法具有更大的灵活性和便利性，可扩展到各种型号扫描仪的校准任务中。我们采用这种方法校准了 GE Typhoon FLA 7000 扫描仪的灵敏度。此外，我们还对 BAS-MS、BAS-SR 和 BAS-TR 型 IP 在 20±1 °C 环境条件下的自发信号衰减行为进行了校准，并观察到 BAS-MS IP 中存在明显的信号载流子扩散行为。校准结果为进一步研究超短、超强激光与物质之间的相互作用奠定了基础。
{"title":"Imaging plate scanners calibration and the attenuation behavior of imaging plate signals","authors":"Nan Bo, Nai-Yan Wang","doi":"10.1088/1674-1056/ad43d4","DOIUrl":"https://doi.org/10.1088/1674-1056/ad43d4","url":null,"abstract":"Based on previously reported work, we propose a new method for calibrating image plate (IP) scanners, offering greater flexibility and convenience, which can be extended to the calibration tasks of various scanner models. This method was applied to calibrate the sensitivity of a GE Typhoon FLA 7000 scanner. Additionally, we performed a calibration of the spontaneous signal attenuation behavior for BAS-MS, BAS-SR, and BAS-TR type IPs under the 20±1 °C environmental conditions, and observed significant signal carrier diffusion behavior in BAS-MS IP. The calibration results lay a foundation for further research on the interaction between ultra-short, ultra-intense lasers and matter.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-06-01DOI: 10.1088/0256-307x/41/6/064201
Bo-Hao Wu, Xin-Xin Yang, Yu Chen, Wei Zhang
We study superradiant phase transitions in a hybrid system of a two-dimensional Bose–Einstein condensate of atoms and two cavities arranged with a tilt angle. By adjusting the loss rate of cavities, we map out the phase diagram of steady states within a mean field framework. It is found that when the loss rates of the two cavities are different, superradiant transitions may not occur at the same time in the two cavities. A first-order phase transition is observed between the states with only one cavity in superradiance and both in superradiance. In the case that both cavities are superradiant, a net photon current is observed flowing from the cavity with small decay rate to the one with large decay rate. The photon current shows a non-monotonic dependence on the loss rate difference, owing to the competition of photon number difference and cavity field phase difference. Our findings can be realized and detected in experiments.
{"title":"Dissipation-Driven Superradiant Phase Transition of a Two-Dimensional Bose–Einstein Condensate in a Double Cavity","authors":"Bo-Hao Wu, Xin-Xin Yang, Yu Chen, Wei Zhang","doi":"10.1088/0256-307x/41/6/064201","DOIUrl":"https://doi.org/10.1088/0256-307x/41/6/064201","url":null,"abstract":"We study superradiant phase transitions in a hybrid system of a two-dimensional Bose–Einstein condensate of atoms and two cavities arranged with a tilt angle. By adjusting the loss rate of cavities, we map out the phase diagram of steady states within a mean field framework. It is found that when the loss rates of the two cavities are different, superradiant transitions may not occur at the same time in the two cavities. A first-order phase transition is observed between the states with only one cavity in superradiance and both in superradiance. In the case that both cavities are superradiant, a net photon current is observed flowing from the cavity with small decay rate to the one with large decay rate. The photon current shows a non-monotonic dependence on the loss rate difference, owing to the competition of photon number difference and cavity field phase difference. Our findings can be realized and detected in experiments.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"15 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141547979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-05-31DOI: 10.1088/0256-307x/41/7/077103
Yang Zhong, 阳 钟, Hongyu Yu, 宏宇 于, Jihui Yang, 吉辉 杨, Xingyu Guo, 星宇 郭, Hongjun Xiang, 红军 向, Xingao Gong and 新高 龚
While density functional theory (DFT) serves as a prevalent computational approach in electronic structure calculations, its computational demands and scalability limitations persist. Recently, leveraging neural networks to parameterize the Kohn–Sham DFT Hamiltonian has emerged as a promising avenue for accelerating electronic structure computations. Despite advancements, challenges such as the necessity for computing extensive DFT training data to explore each new system and the complexity of establishing accurate machine learning models for multi-elemental materials still exist. Addressing these hurdles, this study introduces a universal electronic Hamiltonian model trained on Hamiltonian matrices obtained from first-principles DFT calculations of nearly all crystal structures on the Materials Project. We demonstrate its generality in predicting electronic structures across the whole periodic table, including complex multi-elemental systems, solid-state electrolytes, Moiré twisted bilayer heterostructure, and metal-organic frameworks. Moreover, we utilize the universal model to conduct high-throughput calculations of electronic structures for crystals in GNoME datasets, identifying 3940 crystals with direct band gaps and 5109 crystals with flat bands. By offering a reliable efficient framework for computing electronic properties, this universal Hamiltonian model lays the groundwork for advancements in diverse fields, such as easily providing a huge data set of electronic structures and also making the materials design across the whole periodic table possible.
{"title":"Universal Machine Learning Kohn–Sham Hamiltonian for Materials","authors":"Yang Zhong, 阳 钟, Hongyu Yu, 宏宇 于, Jihui Yang, 吉辉 杨, Xingyu Guo, 星宇 郭, Hongjun Xiang, 红军 向, Xingao Gong and 新高 龚","doi":"10.1088/0256-307x/41/7/077103","DOIUrl":"https://doi.org/10.1088/0256-307x/41/7/077103","url":null,"abstract":"While density functional theory (DFT) serves as a prevalent computational approach in electronic structure calculations, its computational demands and scalability limitations persist. Recently, leveraging neural networks to parameterize the Kohn–Sham DFT Hamiltonian has emerged as a promising avenue for accelerating electronic structure computations. Despite advancements, challenges such as the necessity for computing extensive DFT training data to explore each new system and the complexity of establishing accurate machine learning models for multi-elemental materials still exist. Addressing these hurdles, this study introduces a universal electronic Hamiltonian model trained on Hamiltonian matrices obtained from first-principles DFT calculations of nearly all crystal structures on the Materials Project. We demonstrate its generality in predicting electronic structures across the whole periodic table, including complex multi-elemental systems, solid-state electrolytes, Moiré twisted bilayer heterostructure, and metal-organic frameworks. Moreover, we utilize the universal model to conduct high-throughput calculations of electronic structures for crystals in GNoME datasets, identifying 3940 crystals with direct band gaps and 5109 crystals with flat bands. By offering a reliable efficient framework for computing electronic properties, this universal Hamiltonian model lays the groundwork for advancements in diverse fields, such as easily providing a huge data set of electronic structures and also making the materials design across the whole periodic table possible.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"8 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-05-01DOI: 10.1088/0256-307x/41/5/059501
Jing-Yu Ran, Bao Wang, Jun-Jie Wei
A hypothetical photon mass mγ can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed distance. The dispersion measure and redshift measurements of fast radio bursts (FRBs) have been widely used to constrain the rest mass of the photon. However, all current studies analyzed the effect of the frequency-dependent dispersion for massive photons in the standard ΛCDM cosmological context. In order to alleviate the circularity problem induced by the presumption of a specific cosmological model based on the fundamental postulate of the masslessness of photons, here we employ a new model-independent smoothing technique, artificial neural network (ANN), to reconstruct the Hubble parameter H(z) function from 34 cosmic-chronometer measurements. By combining observations of 32 well-localized FRBs and the H(z) function reconstructed by ANN, we obtain an upper limit of mγ ≤ 3.5 × 10−51 kg, or equivalently mγ ≤ 2.0 × 10−15 eV/c2 (mγ ≤ 6.5 × 10−51 kg, or equivalently mγ ≤ 3.6 × 10−15 eV/c2) at the 1σ (2σ) confidence level. This is the first cosmology-independent photon mass limit derived from extragalactic sources.
{"title":"Cosmology-Independent Photon Mass Limits from Localized Fast Radio Bursts by Using Artificial Neural Networks","authors":"Jing-Yu Ran, Bao Wang, Jun-Jie Wei","doi":"10.1088/0256-307x/41/5/059501","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/059501","url":null,"abstract":"A hypothetical photon mass <italic toggle=\"yes\">m<sub>γ</sub>\u0000</italic> can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed distance. The dispersion measure and redshift measurements of fast radio bursts (FRBs) have been widely used to constrain the rest mass of the photon. However, all current studies analyzed the effect of the frequency-dependent dispersion for massive photons in the standard ΛCDM cosmological context. In order to alleviate the circularity problem induced by the presumption of a specific cosmological model based on the fundamental postulate of the masslessness of photons, here we employ a new model-independent smoothing technique, artificial neural network (ANN), to reconstruct the Hubble parameter <italic toggle=\"yes\">H</italic>(<italic toggle=\"yes\">z</italic>) function from 34 cosmic-chronometer measurements. By combining observations of 32 well-localized FRBs and the <italic toggle=\"yes\">H</italic>(<italic toggle=\"yes\">z</italic>) function reconstructed by ANN, we obtain an upper limit of <italic toggle=\"yes\">m<sub>γ</sub>\u0000</italic> ≤ 3.5 × 10<sup>−51</sup> kg, or equivalently <italic toggle=\"yes\">m<sub>γ</sub>\u0000</italic> ≤ 2.0 × 10<sup>−15</sup> eV/c<sup>2</sup> (<italic toggle=\"yes\">m<sub>γ</sub>\u0000</italic> ≤ 6.5 × 10<sup>−51</sup> kg, or equivalently <italic toggle=\"yes\">m<sub>γ</sub>\u0000</italic> ≤ 3.6 × 10<sup>−15</sup> eV/c<sup>2</sup>) at the 1<italic toggle=\"yes\">σ</italic> (2<italic toggle=\"yes\">σ</italic>) confidence level. This is the first cosmology-independent photon mass limit derived from extragalactic sources.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"50 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141190321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Rare-earth-free Mn-based binary alloy L10-MnAl with bulk perpendicular magnetic anisotropy (PMA) holds promise for high-performance magnetic random access memory (MRAM) devices driven by spin-orbit torque (SOT). However, the lattice-mismatch issue makes it challenging to place conventional spin current sources, such as heavy metals, between L10-MnAl layers and substrates. In this work, we propose a solution by using the B2-CoGa alloy as the spin current source. The lattice-matching enables high-quality epitaxial growth of 2-nm-thick L10-MnAl on B2-CoGa, and the L10-MnAl exhibits a large PMA constant of 1.04 × 106 J/m3. Subsequently, the considerable spin Hall effect in B2-CoGa enables the achievement of SOT-induced deterministic magnetization switching. Moreover, we quantitatively determine the SOT efficiency in the bilayer. Furthermore, we design an L10-MnAl/B2-CoGa/Co2MnGa structure to achieve field-free magnetic switching. Our results provide valuable insights for achieving high-performance SOT-MRAM devices based on L10-MnAl alloy.
{"title":"Current-Induced Magnetization Switching Behavior in Perpendicular Magnetized L10-MnAl/B2-CoGa Bilayer","authors":"Hong-Li Sun, Rong-Kun Han, Hong-Rui Qin, Xu-Peng Zhao, Zhi-Cheng Xie, Da-Hai Wei, Jian-Hua Zhao","doi":"10.1088/0256-307x/41/5/057503","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057503","url":null,"abstract":"Rare-earth-free Mn-based binary alloy L1<sub>0</sub>-MnAl with bulk perpendicular magnetic anisotropy (PMA) holds promise for high-performance magnetic random access memory (MRAM) devices driven by spin-orbit torque (SOT). However, the lattice-mismatch issue makes it challenging to place conventional spin current sources, such as heavy metals, between L1<sub>0</sub>-MnAl layers and substrates. In this work, we propose a solution by using the B2-CoGa alloy as the spin current source. The lattice-matching enables high-quality epitaxial growth of 2-nm-thick L1<sub>0</sub>-MnAl on B2-CoGa, and the L1<sub>0</sub>-MnAl exhibits a large PMA constant of 1.04 × 10<sup>6</sup> J/m<sup>3</sup>. Subsequently, the considerable spin Hall effect in B2-CoGa enables the achievement of SOT-induced deterministic magnetization switching. Moreover, we quantitatively determine the SOT efficiency in the bilayer. Furthermore, we design an L1<sub>0</sub>-MnAl/B2-CoGa/Co<sub>2</sub>MnGa structure to achieve field-free magnetic switching. Our results provide valuable insights for achieving high-performance SOT-MRAM devices based on L1<sub>0</sub>-MnAl alloy.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"14 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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