Abstract Non-Hermitian Hamiltonians effectively describing the physics of open systems have become an important tool in various physical platforms, such as photonics, mechanical systems, and electric circuits. The study of non-Hermitian states in electric circuits is developing rapidly recently and forming the field of topoelectrical circuits. Here, we report on the theoretical realization of a higher-order exceptional points (EPs) topological circuit induced by gain and loss. It is shown that, by tuning the value of the positive and negative resistors in the circuit, EPs can collide and merge leading to higher-order singularities. We observe the different energy-difference conserving dynamics near the EPs and the enhanced sensitivity at higher-order EPs. Our results show a way to get higher sensitivity in a non-Hermitian electrical circuit.
{"title":"Gain and loss induced higher-order exceptional points in a non-Hermitian electrical circuit","authors":"Xizhou Shen, Keyu Pan, Xiumei Wang, Hengxuan Jiang, Xingping Zhou","doi":"10.1088/1361-6463/ad0989","DOIUrl":"https://doi.org/10.1088/1361-6463/ad0989","url":null,"abstract":"Abstract Non-Hermitian Hamiltonians effectively describing the physics of open systems have become an important tool in various physical platforms, such as photonics, mechanical systems, and electric circuits. The study of non-Hermitian states in electric circuits is developing rapidly recently and forming the field of topoelectrical circuits. Here, we report on the theoretical realization of a higher-order exceptional points (EPs) topological circuit induced by gain and loss. It is shown that, by tuning the value of the positive and negative resistors in the circuit, EPs can collide and merge leading to higher-order singularities. We observe the different energy-difference conserving dynamics near the EPs and the enhanced sensitivity at higher-order EPs. Our results show a way to get higher sensitivity in a non-Hermitian electrical circuit.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":"64 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135091313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Using a convenient and low-cost plasma-enhanced chemical vapor deposition (PECVD) technique, uniform Ga2O3 thin films were hetero-grown on c-plane sapphire substrates at different temperatures, with root mean square (RMS) roughness as low as 2.71 nm and a growth rate of up to 1121.30 nm/h; and then the solar-blind UV photodetection performances were discussed in detail. Metal-semiconductor-metal (MSM) solar-blind UV photodetectors based on the five Ga2O3 films prepared at different temperatures exhibit ultra-low dark currents (Idark) ranging among 22-168 fA. Under the illumination of 254 nm UV light, the photodetector prepared by the film grown at 820 ℃ possesses the highest performance with a high photo-to-dark current ratio (PDCR) of 1.47×105, a low rise/fall time of 0.067/0.13 s, a specific detectivity (D*) of 3.56×1012 Jones, and a linear dynamic range (LDR) of 92.89 dB. In all, the results in this work may well provide a referable method for growing cost-effective and ultralow-noise Ga2O3 thin films; as well as achieving decent solar-blind UV sensing application.
{"title":"Study on the PECVD-hetero-grown β-Ga2O3 thin film and temperature-modulated solar-blind UV photodetection","authors":"Zhaoying Xi, Lili Yang, Zeng Liu, Suhao Yao, Lincong Shu, Maolin Zhang, Shan Li, Yufeng Guo, Weihua Tang","doi":"10.1088/1361-6463/ad0bc4","DOIUrl":"https://doi.org/10.1088/1361-6463/ad0bc4","url":null,"abstract":"Abstract Using a convenient and low-cost plasma-enhanced chemical vapor deposition (PECVD) technique, uniform Ga2O3 thin films were hetero-grown on c-plane sapphire substrates at different temperatures, with root mean square (RMS) roughness as low as 2.71 nm and a growth rate of up to 1121.30 nm/h; and then the solar-blind UV photodetection performances were discussed in detail. Metal-semiconductor-metal (MSM) solar-blind UV photodetectors based on the five Ga2O3 films prepared at different temperatures exhibit ultra-low dark currents (Idark) ranging among 22-168 fA. Under the illumination of 254 nm UV light, the photodetector prepared by the film grown at 820 ℃ possesses the highest performance with a high photo-to-dark current ratio (PDCR) of 1.47×105, a low rise/fall time of 0.067/0.13 s, a specific detectivity (D*) of 3.56×1012 Jones, and a linear dynamic range (LDR) of 92.89 dB. In all, the results in this work may well provide a referable method for growing cost-effective and ultralow-noise Ga2O3 thin films; as well as achieving decent solar-blind UV sensing application.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":"25 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135136320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad090e
Di Chen, Azatuhi Ayrikyan, Xiang-Cheng Chu, Marc Kamlah, Kyle G Webber
Abstract This work explores the creep behavior of polycrystalline 0.91(Na 1/2 Bi 1/2 )TiO 3 -0.06BaTiO 3 -0.03K 0.5 Na 0.5 NbO 3 under constant electric fields. It reveals intriguing time-dependent variations in both polarization and strain response, which can be attributed to a transformation from the relaxor state to a long-range ferroelectric order. Meanwhile, bulk volume resistivity values are obtained to eliminate the influence of leakage current on the polarization assessment. The findings provide valuable insights into the creep behavior of lead-free relaxor ferroelectrics, laying a solid foundation for enhancing the performance and reliability of piezoactuators.
摘要研究了多晶0.91(Na 1/2 Bi 1/2) tio3 -0.06 batio3 -0.03K 0.5 Na 0.5 nbo3在恒电场作用下的蠕变行为。它揭示了极化和应变响应中有趣的随时间变化，这可以归因于从弛豫态到远程铁电态的转变。同时，获得了体体积电阻率值，消除了漏电流对极化评价的影响。研究结果为无铅弛豫铁电体的蠕变行为提供了有价值的见解，为提高压电致动器的性能和可靠性奠定了坚实的基础。
{"title":"Creep in 0.91(Na1/2Bi1/2)TiO3-0.06BaTiO3-0.03K0.5Na0.5NbO3 lead-free piezoceramic under constant electric field loads","authors":"Di Chen, Azatuhi Ayrikyan, Xiang-Cheng Chu, Marc Kamlah, Kyle G Webber","doi":"10.1088/1361-6463/ad090e","DOIUrl":"https://doi.org/10.1088/1361-6463/ad090e","url":null,"abstract":"Abstract This work explores the creep behavior of polycrystalline 0.91(Na 1/2 Bi 1/2 )TiO 3 -0.06BaTiO 3 -0.03K 0.5 Na 0.5 NbO 3 under constant electric fields. It reveals intriguing time-dependent variations in both polarization and strain response, which can be attributed to a transformation from the relaxor state to a long-range ferroelectric order. Meanwhile, bulk volume resistivity values are obtained to eliminate the influence of leakage current on the polarization assessment. The findings provide valuable insights into the creep behavior of lead-free relaxor ferroelectrics, laying a solid foundation for enhancing the performance and reliability of piezoactuators.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad0b54
Yongtao Bai, Xiaolei Li, Yiwen Liao
Abstract This study investigates the transmission characteristics of natural forests with branches and introduces a bio-inspired branch structure seismic metamaterial designed to create bandgaps for low-frequency Rayleigh waves. Employing the finite element method, we reveal the mechanism behind the generation of these Rayleigh wave bandgaps and their transmission properties. A distinct 'collectivization mode' within the bio-inspired branch structure seismic metamaterial is identified, effectively attenuating Rayleigh waves. A collectivization coefficient is introduced for quantitative characterization, and we extend the analysis to multi-layered soil mediums, demonstrating an interface with the metamaterial's bandgaps. Frequency-domain analysis highlights the difference between using the collectivization mode and traditional methods for attenuating surface waves, offering a novel approach to low-frequency Rayleigh wave reduction with implications in seismology and related fields.
{"title":"Bio-inspired branch structure seismic metamaterial: attenuating low-frequency Rayleigh waves","authors":"Yongtao Bai, Xiaolei Li, Yiwen Liao","doi":"10.1088/1361-6463/ad0b54","DOIUrl":"https://doi.org/10.1088/1361-6463/ad0b54","url":null,"abstract":"Abstract This study investigates the transmission characteristics of natural forests with branches and introduces a bio-inspired branch structure seismic metamaterial designed to create bandgaps for low-frequency Rayleigh waves. Employing the finite element method, we reveal the mechanism behind the generation of these Rayleigh wave bandgaps and their transmission properties. A distinct 'collectivization mode' within the bio-inspired branch structure seismic metamaterial is identified, effectively attenuating Rayleigh waves. A collectivization coefficient is introduced for quantitative characterization, and we extend the analysis to multi-layered soil mediums, demonstrating an interface with the metamaterial's bandgaps. Frequency-domain analysis highlights the difference between using the collectivization mode and traditional methods for attenuating surface waves, offering a novel approach to low-frequency Rayleigh wave reduction with implications in seismology and related fields.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 16","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad0b52
Yuan Zhu, Jia-sheng Liang, Xun Shi, Zhen Zhang
Abstract As a synaptic device candidate for artificial neural networks (ANNs), memristor holds great promise for efficient neuromorphic computing. However, commonly used filamentary memristors normally exhibit large cyclic variations due to the stochastic nature of filament formation and ablation, which will inevitably degrade the computing accuracy. Here we demonstrate, in nanoscale Ag2S-based memristors, that resistance-switching (RS) at the contact interface can be a promising solution to reduce cyclic variations. When the Ag2S memristor is operated with filament-free interface RS via Schottky barrier height modification at the contact interface, it shows an ultra-small cycle-to-cycle variation of 1.4% during 104 switching cycles. This is in direct contrast to the variation (28.9%) of filament RS extracted from the same device. Interface RS can also emulate synaptic functions and psychological behavior. Its improved learning ability over filament RS, with a higher saturated accuracy approaching 99.6 %, is finally demonstrated in a simplified ANN.
{"title":"Interface Resistance-Switching with Reduced Cyclic Variations for Reliable Neuromorphic Computing","authors":"Yuan Zhu, Jia-sheng Liang, Xun Shi, Zhen Zhang","doi":"10.1088/1361-6463/ad0b52","DOIUrl":"https://doi.org/10.1088/1361-6463/ad0b52","url":null,"abstract":"Abstract As a synaptic device candidate for artificial neural networks (ANNs), memristor holds great promise for efficient neuromorphic computing. However, commonly used filamentary memristors normally exhibit large cyclic variations due to the stochastic nature of filament formation and ablation, which will inevitably degrade the computing accuracy. Here we demonstrate, in nanoscale Ag2S-based memristors, that resistance-switching (RS) at the contact interface can be a promising solution to reduce cyclic variations. When the Ag2S memristor is operated with filament-free interface RS via Schottky barrier height modification at the contact interface, it shows an ultra-small cycle-to-cycle variation of 1.4% during 104 switching cycles. This is in direct contrast to the variation (28.9%) of filament RS extracted from the same device. Interface RS can also emulate synaptic functions and psychological behavior. Its improved learning ability over filament RS, with a higher saturated accuracy approaching 99.6 %, is finally demonstrated in a simplified ANN.
","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad098a
Rahnuma Rahman, Supriyo Bandyopadhyay
Abstract Spin field effect transistors (SpinFET) are an iconic class of spintronic transistor devices that exploit gate tuned spin-orbit interaction in semiconductor channels interposed between ferromagnetic source and drain contacts to elicit transistor functionality. Recently, a new and different type of SpinFET based on gate tuned strain in quantum materials (e.g. topological insulators) has been proposed and may have interesting analog applications, such as in frequency multiplication, by virtue of its unusual oscillatory transfer characteristic. Here, we propose and analyze yet another type of SpinFET in this class, which may have a different application. It is based on gate-tuned strain in a Weyl semimetal, with the strain modulating spin interference. Because the operating principle is non-classical, the channel conductance shows oscillatory dependence on the channel length at zero gate voltage. Furthermore, the transconductance can switch sign if the channel length is varied. This latter feature can be exploited to implement a complementary device like complementary metal oxide semiconductor (CMOS) by connecting two such SpinFETs of slightly different channel lengths in series. These unusual properties may have niche applications.
{"title":"A Spin Field Effect Transistor Based on a Strained Two Dimensional Layer of a Weyl Semimetal","authors":"Rahnuma Rahman, Supriyo Bandyopadhyay","doi":"10.1088/1361-6463/ad098a","DOIUrl":"https://doi.org/10.1088/1361-6463/ad098a","url":null,"abstract":"Abstract Spin field effect transistors (SpinFET) are an iconic class of spintronic transistor devices that exploit gate tuned spin-orbit interaction in semiconductor channels interposed between ferromagnetic source and drain contacts to elicit transistor functionality. Recently, a new and different type of SpinFET based on gate tuned strain in quantum materials (e.g. topological insulators) has been proposed and may have interesting analog applications, such as in frequency multiplication, by virtue of its unusual oscillatory transfer characteristic. Here, we propose and analyze yet another type of SpinFET in this class, which may have a different application. It is based on gate-tuned strain in a Weyl semimetal, with the strain modulating spin interference. Because the operating principle is non-classical, the channel conductance shows oscillatory dependence on the channel length at zero gate voltage. Furthermore, the transconductance can switch sign if the channel length is varied. This latter feature can be exploited to implement a complementary device like complementary metal oxide semiconductor (CMOS) by connecting two such SpinFETs of slightly different channel lengths in series. These unusual properties may have niche applications.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 36","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad098b
Zhuoao Du, Bin Luo, Kejun Zhu
Abstract The polyvinyl chloride (PVC) gel actuator has the advantages of low mass density, large actuation strain, good compliance, and simple fabrication. It deforms when excited by a voltage, and the deformation amplitude of the actuator is higher when an alternating current voltage of a specific frequency causes the actuator to resonate. In this paper, a circular-plane actuator based on PVC gel film and flexible electrodes was developed. Then, a theoretical model is established based on the Yeoh strain energy density function model and the mechanical analysis of deformation region-boundary constraints, the key parameters affecting the deformation are obtained. Subsequently, finite element simulation tests were done on the basis of this model, and the values of uniaxial stretching were highly consistent with the previous actual experimental results, which verified the reasonableness of the model and simulation method. Then, we focus on the analysis of the resonance frequencies of PVC actuators with different plasticizer content, electrode diameter, and pre-stretching degree. Finally, we compare the differences in time-domain characteristics of PVC actuators in the resonant and non-resonant states.
{"title":"Study on deformation theory and resonance frequency of circular-plane PVC actuator","authors":"Zhuoao Du, Bin Luo, Kejun Zhu","doi":"10.1088/1361-6463/ad098b","DOIUrl":"https://doi.org/10.1088/1361-6463/ad098b","url":null,"abstract":"Abstract The polyvinyl chloride (PVC) gel actuator has the advantages of low mass density, large actuation strain, good compliance, and simple fabrication. It deforms when excited by a voltage, and the deformation amplitude of the actuator is higher when an alternating current voltage of a specific frequency causes the actuator to resonate. In this paper, a circular-plane actuator based on PVC gel film and flexible electrodes was developed. Then, a theoretical model is established based on the Yeoh strain energy density function model and the mechanical analysis of deformation region-boundary constraints, the key parameters affecting the deformation are obtained. Subsequently, finite element simulation tests were done on the basis of this model, and the values of uniaxial stretching were highly consistent with the previous actual experimental results, which verified the reasonableness of the model and simulation method. Then, we focus on the analysis of the resonance frequencies of PVC actuators with different plasticizer content, electrode diameter, and pre-stretching degree. Finally, we compare the differences in time-domain characteristics of PVC actuators in the resonant and non-resonant states.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 35","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad090f
Meghna C H, Don Mathew, Vincent Mathew
Abstract The optical analog of the electromagnetically induced reflectance (EIR) effect was theoretically studied in an active topological photonic structure comprising Dirac semi-metal and topological photonic crystal. The destructive interference between the optical Tamm state and topological edge state results in an induced reflection. It was known that the EIR-like effect occurs in a system having a radiative state and a metastable state. Topological protection is used here to achieve a metastable state, so an effective design of the EIR-like effect was possible. The observed EIR-like effect was modeled as a coupled oscillator system. The use of bulk Dirac semi-metal makes this an active photonic system at terahertz frequencies where the Fermi energy can act as a tunable and controlling parameter through which the induced transparency can be varied.
{"title":"Topologically originated optical analog of electromagnetically induced reflectance in Dirac semi-metal based photonic structure","authors":"Meghna C H, Don Mathew, Vincent Mathew","doi":"10.1088/1361-6463/ad090f","DOIUrl":"https://doi.org/10.1088/1361-6463/ad090f","url":null,"abstract":"Abstract The optical analog of the electromagnetically induced reflectance (EIR) effect was theoretically studied in an active topological photonic structure comprising Dirac semi-metal and topological photonic crystal. The destructive interference between the optical Tamm state and topological edge state results in an induced reflection. It was known that the EIR-like effect occurs in a system having a radiative state and a metastable state. Topological protection is used here to achieve a metastable state, so an effective design of the EIR-like effect was possible. The observed EIR-like effect was modeled as a coupled oscillator system. The use of bulk Dirac semi-metal makes this an active photonic system at terahertz frequencies where the Fermi energy can act as a tunable and controlling parameter through which the induced transparency can be varied.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1088/1361-6463/ad0b53
Raphael Färber, Ondrej Sefl, Christian M Franck
Abstract The partial discharge inception voltage (PDIV) in contacting enameled wire pairs exhibits a marked decrease with increased air humidity. While existing literature mentions several potential mechanisms for this reduction, a comprehensive quantitative assessment of the associated effects is lacking. This research paper addresses this knowledge gap by providing a quantitative estimation of the combined impact of water on the gas's ionization yield (effective ionization coefficient) and the modification of the gap electric field caused by water absorption into the bulk of the insulating coating and the associated microscopic and macroscopic polarization processes (dielectric permittivity). However, a comparison of the theoretical predictions with experimental data reveals that these factors alone cannot fully account for the observed reduction in PDIV. Therefore, the study explores additional mechanisms mentioned in the literature, with particular focus on the development of a semi-conductive layer on the insulation coating in humid atmospheres. The numerical simulations of the surface charge dynamics within this layer suggests that the frequency-dependent decrease in PDIV under high-humidity atmospheres can indeed be attributed to the modification of the gap electric field due to the accumulation of surface charge in the semi-conductive layer.
{"title":"On the influence of humidity on the breakdown strength of air---with a case study on the PDIV of contacting enameled wire pairs","authors":"Raphael Färber, Ondrej Sefl, Christian M Franck","doi":"10.1088/1361-6463/ad0b53","DOIUrl":"https://doi.org/10.1088/1361-6463/ad0b53","url":null,"abstract":"Abstract The partial discharge inception voltage (PDIV) in contacting enameled wire pairs exhibits a marked decrease with increased air humidity. While existing literature mentions several potential mechanisms for this reduction, a comprehensive quantitative assessment of the associated effects is lacking. This research paper addresses this knowledge gap by providing a quantitative estimation of the combined impact of water on the gas's ionization yield (effective ionization coefficient) and the modification of the gap electric field caused by water absorption into the bulk of the insulating coating and the associated microscopic and macroscopic polarization processes (dielectric permittivity). However, a comparison of the theoretical predictions with experimental data reveals that these factors alone cannot fully account for the observed reduction in PDIV. Therefore, the study explores additional mechanisms mentioned in the literature, with particular focus on the development of a semi-conductive layer on the insulation coating in humid atmospheres. The numerical simulations of the surface charge dynamics within this layer suggests that the frequency-dependent decrease in PDIV under high-humidity atmospheres can indeed be attributed to the modification of the gap electric field due to the accumulation of surface charge in the semi-conductive layer.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1088/1361-6463/ad056b
Saurabh S Sharma, Avinash Parashar
Abstract Nuclear structures are prone to irradiation-induced defects that make them susceptible to alternation in mechanical and thermal properties. The transmutation of Ni to insoluble He atoms is considered to be responsible for the embrittlement of Ni. Helium bubbles are deemed responsible for the deterioration of mechanical and thermal properties of the Ni crystal, and this should be studied in detail to predict the lifespan of ageing nuclear structures. The aim of this article is to study the effect of helium on the thermal transport phenomenon in single- and bi-crystals of Ni. Molecular dynamics-based simulations in conjunction with a hybrid force field are performed to study the effect of a helium bubble on the thermal transport phenomenon in Ni crystals. These simulations are further extended to study the impact of symmetrical tilt grain boundaries (STGB) in conjunction with the doping of helium atoms on the thermal transport phenomenon in bi-crystal Ni. The effect of helium concentration in the bubble significantly alters the thermal transport in single-crystal Ni. The STGB configuration also introduces interfacial thermal resistance as a function of the misorientation angle. The helium-doped grain boundaries further increase the resistance to phonon movement and increase Kapitza resistance. The increase in Kapitza resistance is more dominant in higher misorientation angle grain boundaries.
{"title":"Effect of helium on the thermal transport properties in single and bi crystals of Ni: a MD based study","authors":"Saurabh S Sharma, Avinash Parashar","doi":"10.1088/1361-6463/ad056b","DOIUrl":"https://doi.org/10.1088/1361-6463/ad056b","url":null,"abstract":"Abstract Nuclear structures are prone to irradiation-induced defects that make them susceptible to alternation in mechanical and thermal properties. The transmutation of Ni to insoluble He atoms is considered to be responsible for the embrittlement of Ni. Helium bubbles are deemed responsible for the deterioration of mechanical and thermal properties of the Ni crystal, and this should be studied in detail to predict the lifespan of ageing nuclear structures. The aim of this article is to study the effect of helium on the thermal transport phenomenon in single- and bi-crystals of Ni. Molecular dynamics-based simulations in conjunction with a hybrid force field are performed to study the effect of a helium bubble on the thermal transport phenomenon in Ni crystals. These simulations are further extended to study the impact of symmetrical tilt grain boundaries (STGB) in conjunction with the doping of helium atoms on the thermal transport phenomenon in bi-crystal Ni. The effect of helium concentration in the bubble significantly alters the thermal transport in single-crystal Ni. The STGB configuration also introduces interfacial thermal resistance as a function of the misorientation angle. The helium-doped grain boundaries further increase the resistance to phonon movement and increase Kapitza resistance. The increase in Kapitza resistance is more dominant in higher misorientation angle grain boundaries.","PeriodicalId":16833,"journal":{"name":"Journal of Physics D","volume":" 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135293114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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