Pub Date : 2023-12-08DOI: 10.1088/1674-1056/ad1381
Hao-Hang Xu, Qingyuan Liu, Chao Xin, Qin-Xin Shen, Jun Luo, Rui Zhou, Jin-Guang Cheng, Jian Liu, L. L. Tao, Zhi-Guo Liu, Ming-Xue Huo, Xian-Jie Wang, Yu Sui
Quasi-one-dimensional (1D) antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectrum. Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+ occupation, in which the Co2+ ions with S = 3/2 form a 1D spin chain along the a-axis. CoTi2O5 undergoes an antiferromagnetic transition at T N ~ 24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region. Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins, by analyzing the specific heat, the thermal conductivity, and the spin-lattice relaxation rate (1/T 1) as a function of temperature, we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around T N , manifested by the rapid decrease of magnetic specific heat to zero, the double-peak characteristic in thermal conductivity, and the exponential decay of 1/T 1 below T N . Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5, which induces the magnetic anisotropy in CoTi2O5, and then opens the spin gap at low temperature.
{"title":"Spin gap in the quasi-1D S = 3/2 antiferromagnet CoTi2O5","authors":"Hao-Hang Xu, Qingyuan Liu, Chao Xin, Qin-Xin Shen, Jun Luo, Rui Zhou, Jin-Guang Cheng, Jian Liu, L. L. Tao, Zhi-Guo Liu, Ming-Xue Huo, Xian-Jie Wang, Yu Sui","doi":"10.1088/1674-1056/ad1381","DOIUrl":"https://doi.org/10.1088/1674-1056/ad1381","url":null,"abstract":"\u0000 Quasi-one-dimensional (1D) antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectrum. Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+ occupation, in which the Co2+ ions with S = 3/2 form a 1D spin chain along the a-axis. CoTi2O5 undergoes an antiferromagnetic transition at T\u0000 \u0000 N\u0000 ~ 24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region. Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins, by analyzing the specific heat, the thermal conductivity, and the spin-lattice relaxation rate (1/T\u0000 1) as a function of temperature, we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around T\u0000 \u0000 N\u0000 , manifested by the rapid decrease of magnetic specific heat to zero, the double-peak characteristic in thermal conductivity, and the exponential decay of 1/T\u0000 1 below T\u0000 \u0000 N\u0000 . Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5, which induces the magnetic anisotropy in CoTi2O5, and then opens the spin gap at low temperature.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"9 12","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138590145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-06DOI: 10.1088/1674-1056/ad12a9
Shuhang Gong, Ya-ju Li, D. Qian, Jinrui Ye, Kou Zhao, Qiang Zeng, Liangwen Chen, Shaofeng Zhang, Lei Yang, Xinwen Ma
Taking three typical soft samples prepared respectively by loose packings of 72, 100 and 109 μm copper grains as examples, we perform an experiment to investigate the energy dependent laser-induced breakdown spectroscopy (LIBS) of soft materials. We discover a reversal phenomenon in the trend of energy dependence of plasma emission intensity: increasing initially and then decreasing separated by a well-defined critical energy. The trend reversal is attributed to the laser-induced recoil pressure at the critical energy just matching the sample’s yield strength. As a result, a one-to-one correspondence can be well established between the samples’ yield stress and the critical energy that is easily obtainable from LIBS measurements. This allows us to propose an innovative method for estimating the yield stress of soft materials via LIBS with attractive advantages including in-situ remote detection, real-time data collection, and minimal destructive to sample.
{"title":"Estimating the yield stress of soft materials via laser-induced breakdown spectroscopy","authors":"Shuhang Gong, Ya-ju Li, D. Qian, Jinrui Ye, Kou Zhao, Qiang Zeng, Liangwen Chen, Shaofeng Zhang, Lei Yang, Xinwen Ma","doi":"10.1088/1674-1056/ad12a9","DOIUrl":"https://doi.org/10.1088/1674-1056/ad12a9","url":null,"abstract":"\u0000 Taking three typical soft samples prepared respectively by loose packings of 72, 100 and 109 μm copper grains as examples, we perform an experiment to investigate the energy dependent laser-induced breakdown spectroscopy (LIBS) of soft materials. We discover a reversal phenomenon in the trend of energy dependence of plasma emission intensity: increasing initially and then decreasing separated by a well-defined critical energy. The trend reversal is attributed to the laser-induced recoil pressure at the critical energy just matching the sample’s yield strength. As a result, a one-to-one correspondence can be well established between the samples’ yield stress and the critical energy that is easily obtainable from LIBS measurements. This allows us to propose an innovative method for estimating the yield stress of soft materials via LIBS with attractive advantages including in-situ remote detection, real-time data collection, and minimal destructive to sample.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"91 2","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138596114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two types of one-dimensional (1D) anti-$mathcal{PT}$-symmetric periodic ring optical waveguide networks (APTPROWNS), consisting of gain and loss materials, respectively, are constructed in this study. The singular optical propagation properties of these networks are investigated. The results show that that system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection. Conversely, the system composed of loss materials demonstrates equal transmittance and reflectance at some frequency position. In both systems, a new type of total reflection phenomenon is observed. When the imaginary part of the refractive indices of waveguide segments is smaller than $10^{-5}$, the system shows bidirectional transparency with the transmittance tending to be 1and reflectivity be smaller than $10^{-8}$ at some bands, while when the refractive indices of the waveguide segments is real, the system will be bidirectional transparent at the full band. These findings may deepen the understanding of anti-$mathcal{PT}$-symmetric optical systems and optical waveguide networks, and possess potential applications in efficient optical energy storage, ultra-sensitive optical filters, ultra-sensitive all-optical switches, integrated optical chips, stealth physics, and so on.
{"title":"Singular optical propagation properties of two types of one-dimensional anti-$mathcal{PT}$-symmetric periodic ring optical waveguide networks","authors":"Yanglong Fan, Xiangbo Yang, Huada Lian, Runkai Chen, Pengbo Zhu, Dongmei Deng, Hongzhan Liu, Zhongchao Wei","doi":"10.1088/1674-1056/ad12ab","DOIUrl":"https://doi.org/10.1088/1674-1056/ad12ab","url":null,"abstract":"\u0000 Two types of one-dimensional (1D) anti-$mathcal{PT}$-symmetric periodic ring optical waveguide networks (APTPROWNS), consisting of gain and loss materials, respectively, are constructed in this study. The singular optical propagation properties of these networks are investigated. The results show that that system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection. Conversely, the system composed of loss materials demonstrates equal transmittance and reflectance at some frequency position. In both systems, a new type of total reflection phenomenon is observed. When the imaginary part of the refractive indices of waveguide segments is smaller than $10^{-5}$, the system shows bidirectional transparency with the transmittance tending to be 1and reflectivity be smaller than $10^{-8}$ at some bands, while when the refractive indices of the waveguide segments is real, the system will be bidirectional transparent at the full band. These findings may deepen the understanding of anti-$mathcal{PT}$-symmetric optical systems and optical waveguide networks, and possess potential applications in efficient optical energy storage, ultra-sensitive optical filters, ultra-sensitive all-optical switches, integrated optical chips, stealth physics, and so on.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"9 3","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138594391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-06DOI: 10.1088/1674-1056/ad12aa
Zhigang Zheng, Feifei Han, Le Wang, Shengmei Zhao
Orbital angular momentum (OAM) holography has become a promising technique in information encryption, data storage and opto-electronic computing, owing to the infinite topological charge of one single OAMmode and the orthogonality of different OAM modes. In this paper, we propose a novel OAM hologramgeneration method based on a densely connected U-Net (DCU), where the densely connected convolutionblocks (DCB) replace the convolution blocks of the U-Net. Importantly, the reconstruction process of theOAM hologram is integrated into DCU as its output layer, so as to eliminate the requirement to preparetraining data for the OAM hologram, which is required by conventional neural networks through an iterative algorithm. The experimental and simulation results show that the OAM hologram can rapidly begenerated with the well-trained DCU, and the reconstructed image’s quality from the generated OAM hologram is significantly improved in comparison with those from the Gerchberg-Saxton generation method, theGerchberg-Saxton based generation method and the U-Net method. In addition, a 10-bit OAM multiplexinghologram scheme is numerically demonstrated to have a high capacity with OAM hologram.
{"title":"Generation of Orbital Angular Momentum Hologram using a Modified U-Net","authors":"Zhigang Zheng, Feifei Han, Le Wang, Shengmei Zhao","doi":"10.1088/1674-1056/ad12aa","DOIUrl":"https://doi.org/10.1088/1674-1056/ad12aa","url":null,"abstract":"\u0000 Orbital angular momentum (OAM) holography has become a promising technique in information encryption, data storage and opto-electronic computing, owing to the infinite topological charge of one single OAMmode and the orthogonality of different OAM modes. In this paper, we propose a novel OAM hologramgeneration method based on a densely connected U-Net (DCU), where the densely connected convolutionblocks (DCB) replace the convolution blocks of the U-Net. Importantly, the reconstruction process of theOAM hologram is integrated into DCU as its output layer, so as to eliminate the requirement to preparetraining data for the OAM hologram, which is required by conventional neural networks through an iterative algorithm. The experimental and simulation results show that the OAM hologram can rapidly begenerated with the well-trained DCU, and the reconstructed image’s quality from the generated OAM hologram is significantly improved in comparison with those from the Gerchberg-Saxton generation method, theGerchberg-Saxton based generation method and the U-Net method. In addition, a 10-bit OAM multiplexinghologram scheme is numerically demonstrated to have a high capacity with OAM hologram.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"63 11","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138594591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 10.1088/1674-1056/ad123e
Pengyu Wei, Chaowen Huang, Xinlu Cheng, Hong Zhang
Cross sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide (CO) by low-energy electron-impact are computed using R-matrix method. The excitation cross sections from the ground state to the electronic states a 3Π, a'3Σ+ and A 1Π agree with previously experimental and theoretical results. Additionally, the cross sections for I 1Σ- and D 1Δ states of CO which will cascade to CO a'3Σ+ and A 1Π states are calculated. What’s more, in contrast to the typical increase in electronic excitation cross sections with collision energy, the de-excitation cross sections show a negative trend with increasing energy.
{"title":"Low energy inelastic electron scattering from carbon monoxide: Excitation and de-excitation of the <i>X</i>\u0000 <sup>1</sup>Σ<sup>+</sup>, <i>a</i>\u0000 <sup>3</sup>Π， <i>a</i>'<sup>3</sup>Σ<sup>+</sup>, <i>A</i>\u0000 <sup>1</sup>Π, <i>d</i>\u0000 ","authors":"Pengyu Wei, Chaowen Huang, Xinlu Cheng, Hong Zhang","doi":"10.1088/1674-1056/ad123e","DOIUrl":"https://doi.org/10.1088/1674-1056/ad123e","url":null,"abstract":"\u0000 Cross sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide (CO) by low-energy electron-impact are computed using R-matrix method. The excitation cross sections from the ground state to the electronic states a\u0000 3Π, a'3Σ+ and A\u0000 1Π agree with previously experimental and theoretical results. Additionally, the cross sections for I\u0000 1Σ- and D\u0000 1Δ states of CO which will cascade to CO a'3Σ+ and A\u0000 1Π states are calculated. What’s more, in contrast to the typical increase in electronic excitation cross sections with collision energy, the de-excitation cross sections show a negative trend with increasing energy.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"10 4","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138598274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts, but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unclear. By using time-dependent density functional theory (TDDFT), we analyze the real-time reaction processes of plasmon-mediated H2 splitting on linear Ag-Au alloy chains when exposed to femtosecond laser pulses. It is found that H2 splitting rate depends on the position and proportion of Au atoms in alloy chains, which indicates that specially designed Ag-Au alloy is more likely to induce the reaction than pure Ag chain. Especially, more electrons directly transfer from the alloy chain to the anti-bonding state of H2, thereby accelerating the H2 splitting reaction. These results establish a theoretical foundation for comprehending the microscopic mechanism of plasmon-induced chemical reaction on the alloy nanostructures.
{"title":"Microscopic mechanism of plasmon-mediated photocatalytic H2 splitting on Ag-Au alloy chain","authors":"Yuhui Song, Yirui Lu, Axin Guo, Yifei Cao, Jinping Li, Zhengkun Fu, Lei Yan, Zhenglong Zhang","doi":"10.1088/1674-1056/ad123d","DOIUrl":"https://doi.org/10.1088/1674-1056/ad123d","url":null,"abstract":"\u0000 Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts, but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unclear. By using time-dependent density functional theory (TDDFT), we analyze the real-time reaction processes of plasmon-mediated H2 splitting on linear Ag-Au alloy chains when exposed to femtosecond laser pulses. It is found that H2 splitting rate depends on the position and proportion of Au atoms in alloy chains, which indicates that specially designed Ag-Au alloy is more likely to induce the reaction than pure Ag chain. Especially, more electrons directly transfer from the alloy chain to the anti-bonding state of H2, thereby accelerating the H2 splitting reaction. These results establish a theoretical foundation for comprehending the microscopic mechanism of plasmon-induced chemical reaction on the alloy nanostructures.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"139 15","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138598902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-04DOI: 10.1088/1674-1056/ad11e7
Yun-Hong Zhang, Chong Liu
We study the nonlinear stage of modulation instability (MI) in the non-intergrable pure-quartic nonlinear Schrödinger equation where the fourth-order dispersion is modulated periodically. Using the three-mode truncation, we reveal the complex recurrence of parametric resonance (PR) breathers, where each recurrence is associated with two oscillation periods (PR period and internal oscillation period). The nonlinear stage of parametric instability admits the maximum energy exchange between the spectrum sidebands and central mode occurring outside the MI gain band.
{"title":"Parametric instability in the pure-quartic nonlinear Schrödinger equation","authors":"Yun-Hong Zhang, Chong Liu","doi":"10.1088/1674-1056/ad11e7","DOIUrl":"https://doi.org/10.1088/1674-1056/ad11e7","url":null,"abstract":"\u0000 We study the nonlinear stage of modulation instability (MI) in the non-intergrable pure-quartic nonlinear Schrödinger equation where the fourth-order dispersion is modulated periodically. Using the three-mode truncation, we reveal the complex recurrence of parametric resonance (PR) breathers, where each recurrence is associated with two oscillation periods (PR period and internal oscillation period). The nonlinear stage of parametric instability admits the maximum energy exchange between the spectrum sidebands and central mode occurring outside the MI gain band.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"16 6","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138603109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-04DOI: 10.1088/1674-1056/ad11e6
Guo-Hui Yu, Hong-Li Yang
This paper introduces the quantum control of Lyapunov functions based on state distance, Lyapunov functions based on the mean of imaginary quantities, and Lyapunov functions based on state errors. In this paper, the specific control laws under the three forms are given, and the stability analysis is analyzed by the LaSalle invariance principle, and the numerical simulation is carried out in the 2D test system. For the Lyapunov function based on the average of virtual mechanical quantities, the particle swarm algorithm and simulated annealing algorithm are combined with the analysis in the calculation process. Finally, a unified form of control law under the three forms is given.
{"title":"Quantum control based on three forms of Lyapunov functions","authors":"Guo-Hui Yu, Hong-Li Yang","doi":"10.1088/1674-1056/ad11e6","DOIUrl":"https://doi.org/10.1088/1674-1056/ad11e6","url":null,"abstract":"\u0000 This paper introduces the quantum control of Lyapunov functions based on state distance, Lyapunov functions based on the mean of imaginary quantities, and Lyapunov functions based on state errors. In this paper, the specific control laws under the three forms are given, and the stability analysis is analyzed by the LaSalle invariance principle, and the numerical simulation is carried out in the 2D test system. For the Lyapunov function based on the average of virtual mechanical quantities, the particle swarm algorithm and simulated annealing algorithm are combined with the analysis in the calculation process. Finally, a unified form of control law under the three forms is given.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"54 8","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138602059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-04DOI: 10.1088/1674-1056/ad11e5
Yi Nie, Guihua Tang, Yifei Li, Min Zhang, Xin Zhao
The zinc oxide (ZnO) shows a great potential in electronics, while the large intrinsic thermal conductivity limits its thermoelectric applications. In this work, we explored the significant carrier transport capacity and diameter dependent thermoelectric characteristics of wurtzite-ZnO<0001> nanowires based on the first principles simulation and molecular dynamics simulation. Under the synergistic effect of band degeneracy and weak phonon-electron scattering, P-type (ZnO)73 nanowires achieve an ultra-high power factor above 1500 μW·cm-1·K-2 in a wide temperature range. The lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size dependence. When the ZnO nanowire diameter exceeds 12.72 Å, the carrier transport properties increase significantly, while the thermal conductivity shows a slight increase with the diameter size, resulting in a ZT value up to 6.4 at 700 K for P-type (ZnO)73. The size effect is also illustrated by introducing two geometrical configuration models of ZnO nanowires for the first time. This work can theoretically depict the strategy of size optimization for thermoelectric conversion of ZnO nanowires.
{"title":"Diameter Dependent Ultra-High Thermoelectric Performance of ZnO Nanowires","authors":"Yi Nie, Guihua Tang, Yifei Li, Min Zhang, Xin Zhao","doi":"10.1088/1674-1056/ad11e5","DOIUrl":"https://doi.org/10.1088/1674-1056/ad11e5","url":null,"abstract":"The zinc oxide (ZnO) shows a great potential in electronics, while the large intrinsic thermal conductivity limits its thermoelectric applications. In this work, we explored the significant carrier transport capacity and diameter dependent thermoelectric characteristics of wurtzite-ZnO<0001> nanowires based on the first principles simulation and molecular dynamics simulation. Under the synergistic effect of band degeneracy and weak phonon-electron scattering, P-type (ZnO)73 nanowires achieve an ultra-high power factor above 1500 μW·cm-1·K-2 in a wide temperature range. The lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size dependence. When the ZnO nanowire diameter exceeds 12.72 Å, the carrier transport properties increase significantly, while the thermal conductivity shows a slight increase with the diameter size, resulting in a ZT value up to 6.4 at 700 K for P-type (ZnO)73. The size effect is also illustrated by introducing two geometrical configuration models of ZnO nanowires for the first time. This work can theoretically depict the strategy of size optimization for thermoelectric conversion of ZnO nanowires.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":"10 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138602933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1674-1056/ad117d
Chang Niu, Sixia Yu
Holevo bound plays an important role in quantum metrology as it sets the ultimate limit for multi-parameter estimations, which can be asymptotically achieved. Except for some trivial cases, the Holevo bound is implicitly defined and formulated with the help of weight matrices. Here we report the first instance of an intrinsic Holevo bound, namely, without any reference to weight matrices, in a nontrivial case. Specifically, we prove that the Holevo bound for estimating two parameters of a qubit is equivalent to the joint constraint imposed by two quantum Cramér-Rao bounds corresponding to symmetric and right logarithmic derivatives. This weightless form of Holevo bound enables us to determine the precise range of independent entries of the mean-square error matrix, i.e., two variances and one covariance that quantify the precisions of the estimation, as illustrated by different estimation models. Our result shed some new light to the relations between the Holevo bound and quantum Cramér-Rao bounds. Possible generalizations are discussed.
{"title":"Holevo bound independent of weight matrices for estimating two parameters of a qubit","authors":"Chang Niu, Sixia Yu","doi":"10.1088/1674-1056/ad117d","DOIUrl":"https://doi.org/10.1088/1674-1056/ad117d","url":null,"abstract":"\u0000 Holevo bound plays an important role in quantum metrology as it sets the ultimate limit for multi-parameter estimations, which can be asymptotically achieved. Except for some trivial cases, the Holevo bound is implicitly defined and formulated with the help of weight matrices. Here we report the first instance of an intrinsic Holevo bound, namely, without any reference to weight matrices, in a nontrivial case. Specifically, we prove that the Holevo bound for estimating two parameters of a qubit is equivalent to the joint constraint imposed by two quantum Cramér-Rao bounds corresponding to symmetric and right logarithmic derivatives. This weightless form of Holevo bound enables us to determine the precise range of independent entries of the mean-square error matrix, i.e., two variances and one covariance that quantify the precisions of the estimation, as illustrated by different estimation models. Our result shed some new light to the relations between the Holevo bound and quantum Cramér-Rao bounds. Possible generalizations are discussed.","PeriodicalId":10253,"journal":{"name":"Chinese Physics B","volume":" 20","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138612698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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