The generalized α-model for anisotropic two-band superconductivity is consistently constructed with the consideration of weak interband electron–electron interaction.Tailored from the two-band BCS theory,the develop...The generalized α-model for anisotropic two-band superconductivity is consistently constructed with the consideration of weak interband electron–electron interaction.Tailored from the two-band BCS theory,the developed framework can be applied to investigate thermodynamic properties of intraband strong-coupling superconductors.Accordingly,we perform a calculation on the temperature dependence of specific heat and obtain an analytic expression for specific heat jump at the superconducting critical temperature.Meanwhile,we also compute the superfluid density and the spin susceptibility with this formalism.Given the low-temperature superconducting gaps from experimental measurement,all of our theoretical results can fit the experimental data of the layered two-band superconductor NbSe_(2) well.展开更多
Based on Ginzburg-Landau theory,we investigate the electromagnetic properties of two-band superconductors with broken time-reversal symmetry.We propose an apparatus of a superconducting ring integrated with a microbri...Based on Ginzburg-Landau theory,we investigate the electromagnetic properties of two-band superconductors with broken time-reversal symmetry.We propose an apparatus of a superconducting ring integrated with a microbridge structure to probe the peculiar topological excitations in the chiral system.The phase difference of two order parameters in the superconductor satisfies the double sine-Gordon equation,and a linear relationship between the phase difference at the two ends of the junction and the total magnetic flux in the ring can be obtained.Then with the Josephson current-phase relation,we establish the dependence of the circulating current and magnetic flux on the applied external magnetic field.Our results show that this single-junction system will exhibit the irreversible behaviors and two different types of fractional flux transitions can clearly manifest the time-reversal symmetry breaking in two-component superconductors.展开更多
Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)...Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.展开更多
The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginz...The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 （T） is increased, while the London penetration depth anisotropy γλ（T） reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.展开更多
Temperature dependence of tbe pair-breaking critical current density of MgB2, jd（T）, is studied using a two-band Ginzburg-Landau theory. The results are shown to be in good agreement with experimental data for the s...Temperature dependence of tbe pair-breaking critical current density of MgB2, jd（T）, is studied using a two-band Ginzburg-Landau theory. The results are shown to be in good agreement with experimental data for the superconducting magnesium diboride MgB2.展开更多
Temperature dependence of the magnetization M （T） of two-band superconductors is studied in the vicinity of upper critical field He2 by using a two-band Ginzburg-Landau （GL） theory. It is shown that magnetization ...Temperature dependence of the magnetization M （T） of two-band superconductors is studied in the vicinity of upper critical field He2 by using a two-band Ginzburg-Landau （GL） theory. It is shown that magnetization M（T） has a nonlinear character due to positive curvature of upper critical field Hc2（T） and temperature dependence of effective Ginzburg-Landau parameter Neff（T）. The results are shown to be in qualitative agreement with experimental data for the superconducting magnesium diboride, MgB2.展开更多
In the present paper, we investigate the existence of ferromagnetism in a two-band Hubbard model, by applying a recently-introduced method by us to study ferromagnetism in metallic dusters. We prove rigorously that th...In the present paper, we investigate the existence of ferromagnetism in a two-band Hubbard model, by applying a recently-introduced method by us to study ferromagnetism in metallic dusters. We prove rigorously that the ground state of this model is ferromagnetic if the intra-orbital Coulomb repulsion between electrons is infinitely strong and only one hole exists in the system. Our theorem improves a previous result. Furthermore, our method can also be applied to dead with the case of multiple holes.展开更多
Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is cal...Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is calculated by using the optimized self-consistent perturbation approach and the results are applied to analyze the thermodynamic data of the iron-based superconductors Ba（1-x）KxFe2As2 with x -0.4, which have been suggested to have a two-band structure by recent experiments. We estimate the fluctuation strength in this material and find that the specific heat is described well with the Ginzburg number Gi = 4 · 10^-4. The influence of interband coupling strength is investigated and the result of the two-band Gaussian approximation approach is compared.展开更多
Many sampling formulas are available for processes in baseband (-a,a) at the Nyquist rate a/π. However signals of telecommunications have power spectra which occupate two bands or more. We know that PNS (periodic non...Many sampling formulas are available for processes in baseband (-a,a) at the Nyquist rate a/π. However signals of telecommunications have power spectra which occupate two bands or more. We know that PNS (periodic non-uniform sampling) allow an errorless reconstruction at rate smaller than the Nyquist one. For instance PNS2 can be used in the two-bands case (-a,-b)∪(b,a) at the Landau rate (a-b)/π We prove a set of formulas which are available in cases more general than the PNS2. They take into account two sampling sequences which can be periodic or not and with same mean rate or not.展开更多
We study the dynamics of an electron spin state transfer along a half-filled two-band model(TBM).It is shown that this solvable and realistic medium has an energy gap between the ground and first-excited states in the...We study the dynamics of an electron spin state transfer along a half-filled two-band model(TBM).It is shown that this solvable and realistic medium has an energy gap between the ground and first-excited states in the half-filled case.By connecting two qubits to two sites of the TBM,the system can accomplish a high-fidelity and long-distance quantum state transfer(QST).Moreover,numerical simulations have been performed for a finite system.The results show that the numerical and analytical results of the effective coupling strength agree well with each other.Furthermore,the investigation shows that the reduced density matrix also has high fidelity beyond the range of perturbation.展开更多
针对基于双向测距(Two Way Ranging,TWR)的超宽带(Ultra Wide Band,UWB)定位技术在温室场景下定位精度较低的问题,提出了一种基于多维处理的TWR测距优化方法,并在此基础上采用差分定位对UWB在温室场景下的定位误差进行修正。基于多维处...针对基于双向测距(Two Way Ranging,TWR)的超宽带(Ultra Wide Band,UWB)定位技术在温室场景下定位精度较低的问题,提出了一种基于多维处理的TWR测距优化方法,并在此基础上采用差分定位对UWB在温室场景下的定位误差进行修正。基于多维处理的TWR测距优化,主要以外推拟合的方式减少TWR测距的异常值,并利用粒子滤波对TWR测距系统的有色噪声进行处理。通过试验与传统的均值滤波和卡尔曼滤波进行对比发现:相较于均值滤波,本文方法的最大误差、误差均值、误差标准差分别降低了69.3%、73.8%、72.1%。基于差分定位的UWB优化方法,通过在常规三边定位的基础上引入位置已知的修正标签,将修正标签在UWB坐标系下到达各个固定基站的测量值与真实值的偏差作为修正值,利用固定基站将修正信息传送给待测标签,并对待测标签位置信息进行误差修正。试验结果表明:本文方法能在一定程度上提高UWB在温室场景下的定位精度。修正后,静态定位下的最大误差、平均绝对误差和均方根误差分别降低了11.56%、12.23%、11.57%,动态定位下的偏差均值、方差和标准差分别降低了9.06%、15.04%和7.84%。展开更多
The salt-inclusion materials have drawn significant attention for their manifold structural chemistry and novel physical/chemical properties.Herein,two new salt-inclusion chalcohalides,[Cs_(6)Cl][Ga_(5)GeQ_(12)](Q=S,S...The salt-inclusion materials have drawn significant attention for their manifold structural chemistry and novel physical/chemical properties.Herein,two new salt-inclusion chalcohalides,[Cs_(6)Cl][Ga_(5)GeQ_(12)](Q=S,Se),have been discovered via hightemperature flux methods.The two isostructural compounds are constructed by porous[Ga_(5)GeQ_(12)]^(5−)layers with[ClCs_(6)]^(5+)octahedra filled in the holes.The[Ga_(5)GeQ_(12)]^(5−)layer is composed of the honeycomb-like(Ga/Ge)_(18)Q_(42)rings containing(Ga/Ge)_(3)Q_(9)trimer as basic unit.The band gaps of the two compounds are 3.90 and 2.89 eV,respectively.[Cs_(6)Cl][Ga_(5)GeS_(12)]exhibits interesting two-band emission properties which are related to the intermediate-band electronic structure revealed by density functional theory(DFT)calculations.Owing to the porous layered structure,[Cs_(6)Cl][Ga_(5)GeS_(12)]exhibits topological ion exchange ability towards Cd^(2+)ions with the maximum sorption capacity of 250 mg/g and high distribution coefficient(Kd)near 106 mL/g.This work further enriches the structural diversity of salt-inclusion materials and extends their potential application range to ion exchange adsorption.展开更多
To compare the ability of three different reconstruction procedures in restoring the posterior displacement of tibia and the posterior stability of the knee joint from 0° to 120°flexion. Methods ： Three po...To compare the ability of three different reconstruction procedures in restoring the posterior displacement of tibia and the posterior stability of the knee joint from 0° to 120°flexion. Methods ： Three posterior cruciate ligaments （PCL） reconstruction procedures were performed, namely two-band two-tunnel reconstruction, one-band anterior tunnel reconstruction and one-band posterior tunnel reconstruction. The posterior displacement of the tibia in relation to the femur was measured when a 200N posterior force was applied. Results： Within the flexion range of 0° to 30°, the displacement in the one-band posterior tunnel reconstruction showed little difference from that of an intact knee （P〉0.05）. But when the flexion exceeded 30°, especially when it exceeded 60°, the displacement in oneband posterior tunnel reconstruction was much greater than that of an intact knee （P〈0.01）. In two-band two-tunnel reconstruction and one-band anterior tunnel reconstruction, the displacement was approximately the same as that of an intact knee ranging from 0° to 120° （P〉0.05）, while a slight over-restriction might be found at some angles. Conclusions： Two-band reconstruction could effectively restrict the posterior displacement of the tibia and restore anterior, posterior stability of the knee joint within its full range of flexion. One-band anterior tunnel reconstruction also could maintain the posterior stability of the knee, while the result of one-band posterior tunnel reconstruction is the most unsatisfactory.展开更多
文摘The generalized α-model for anisotropic two-band superconductivity is consistently constructed with the consideration of weak interband electron–electron interaction.Tailored from the two-band BCS theory,the developed framework can be applied to investigate thermodynamic properties of intraband strong-coupling superconductors.Accordingly,we perform a calculation on the temperature dependence of specific heat and obtain an analytic expression for specific heat jump at the superconducting critical temperature.Meanwhile,we also compute the superfluid density and the spin susceptibility with this formalism.Given the low-temperature superconducting gaps from experimental measurement,all of our theoretical results can fit the experimental data of the layered two-band superconductor NbSe_(2) well.
文摘Based on Ginzburg-Landau theory,we investigate the electromagnetic properties of two-band superconductors with broken time-reversal symmetry.We propose an apparatus of a superconducting ring integrated with a microbridge structure to probe the peculiar topological excitations in the chiral system.The phase difference of two order parameters in the superconductor satisfies the double sine-Gordon equation,and a linear relationship between the phase difference at the two ends of the junction and the total magnetic flux in the ring can be obtained.Then with the Josephson current-phase relation,we establish the dependence of the circulating current and magnetic flux on the applied external magnetic field.Our results show that this single-junction system will exhibit the irreversible behaviors and two different types of fractional flux transitions can clearly manifest the time-reversal symmetry breaking in two-component superconductors.
基金National Natural Science Foundation of China(T2125008,92263108,92163203,52102292,52003198)Shanghai Rising-Star Program(23QA1409300)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-07-E00096)。
文摘Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.
文摘The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 （T） is increased, while the London penetration depth anisotropy γλ（T） reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.
基金NATO reintegration grant，TUBITAK research Foundation
文摘Temperature dependence of tbe pair-breaking critical current density of MgB2, jd（T）, is studied using a two-band Ginzburg-Landau theory. The results are shown to be in good agreement with experimental data for the superconducting magnesium diboride MgB2.
文摘Temperature dependence of the magnetization M （T） of two-band superconductors is studied in the vicinity of upper critical field He2 by using a two-band Ginzburg-Landau （GL） theory. It is shown that magnetization M（T） has a nonlinear character due to positive curvature of upper critical field Hc2（T） and temperature dependence of effective Ginzburg-Landau parameter Neff（T）. The results are shown to be in qualitative agreement with experimental data for the superconducting magnesium diboride, MgB2.
基金Supported by National Natural Science Foundation of China under Grant No.11374017
文摘In the present paper, we investigate the existence of ferromagnetism in a two-band Hubbard model, by applying a recently-introduced method by us to study ferromagnetism in metallic dusters. We prove rigorously that the ground state of this model is ferromagnetic if the intra-orbital Coulomb repulsion between electrons is infinitely strong and only one hole exists in the system. Our theorem improves a previous result. Furthermore, our method can also be applied to dead with the case of multiple holes.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674007)
文摘Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is calculated by using the optimized self-consistent perturbation approach and the results are applied to analyze the thermodynamic data of the iron-based superconductors Ba（1-x）KxFe2As2 with x -0.4, which have been suggested to have a two-band structure by recent experiments. We estimate the fluctuation strength in this material and find that the specific heat is described well with the Ginzburg number Gi = 4 · 10^-4. The influence of interband coupling strength is investigated and the result of the two-band Gaussian approximation approach is compared.
文摘Many sampling formulas are available for processes in baseband (-a,a) at the Nyquist rate a/π. However signals of telecommunications have power spectra which occupate two bands or more. We know that PNS (periodic non-uniform sampling) allow an errorless reconstruction at rate smaller than the Nyquist one. For instance PNS2 can be used in the two-bands case (-a,-b)∪(b,a) at the Landau rate (a-b)/π We prove a set of formulas which are available in cases more general than the PNS2. They take into account two sampling sequences which can be periodic or not and with same mean rate or not.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10874091,2006CB921205,and 108471507)Shandong Provincial Natural Science Foundation,China (Grant No.ZR2009AM026)
文摘We study the dynamics of an electron spin state transfer along a half-filled two-band model(TBM).It is shown that this solvable and realistic medium has an energy gap between the ground and first-excited states in the half-filled case.By connecting two qubits to two sites of the TBM,the system can accomplish a high-fidelity and long-distance quantum state transfer(QST).Moreover,numerical simulations have been performed for a finite system.The results show that the numerical and analytical results of the effective coupling strength agree well with each other.Furthermore,the investigation shows that the reduced density matrix also has high fidelity beyond the range of perturbation.
文摘针对基于双向测距(Two Way Ranging,TWR)的超宽带(Ultra Wide Band,UWB)定位技术在温室场景下定位精度较低的问题,提出了一种基于多维处理的TWR测距优化方法,并在此基础上采用差分定位对UWB在温室场景下的定位误差进行修正。基于多维处理的TWR测距优化,主要以外推拟合的方式减少TWR测距的异常值,并利用粒子滤波对TWR测距系统的有色噪声进行处理。通过试验与传统的均值滤波和卡尔曼滤波进行对比发现:相较于均值滤波,本文方法的最大误差、误差均值、误差标准差分别降低了69.3%、73.8%、72.1%。基于差分定位的UWB优化方法,通过在常规三边定位的基础上引入位置已知的修正标签,将修正标签在UWB坐标系下到达各个固定基站的测量值与真实值的偏差作为修正值,利用固定基站将修正信息传送给待测标签,并对待测标签位置信息进行误差修正。试验结果表明:本文方法能在一定程度上提高UWB在温室场景下的定位精度。修正后,静态定位下的最大误差、平均绝对误差和均方根误差分别降低了11.56%、12.23%、11.57%,动态定位下的偏差均值、方差和标准差分别降低了9.06%、15.04%和7.84%。
基金supported by the National Natural Science Foundation of China (22005006,21871008,22001263)the China Postdoctoral Science Foundation (2019M660298,2020T130009)
文摘The salt-inclusion materials have drawn significant attention for their manifold structural chemistry and novel physical/chemical properties.Herein,two new salt-inclusion chalcohalides,[Cs_(6)Cl][Ga_(5)GeQ_(12)](Q=S,Se),have been discovered via hightemperature flux methods.The two isostructural compounds are constructed by porous[Ga_(5)GeQ_(12)]^(5−)layers with[ClCs_(6)]^(5+)octahedra filled in the holes.The[Ga_(5)GeQ_(12)]^(5−)layer is composed of the honeycomb-like(Ga/Ge)_(18)Q_(42)rings containing(Ga/Ge)_(3)Q_(9)trimer as basic unit.The band gaps of the two compounds are 3.90 and 2.89 eV,respectively.[Cs_(6)Cl][Ga_(5)GeS_(12)]exhibits interesting two-band emission properties which are related to the intermediate-band electronic structure revealed by density functional theory(DFT)calculations.Owing to the porous layered structure,[Cs_(6)Cl][Ga_(5)GeS_(12)]exhibits topological ion exchange ability towards Cd^(2+)ions with the maximum sorption capacity of 250 mg/g and high distribution coefficient(Kd)near 106 mL/g.This work further enriches the structural diversity of salt-inclusion materials and extends their potential application range to ion exchange adsorption.
文摘To compare the ability of three different reconstruction procedures in restoring the posterior displacement of tibia and the posterior stability of the knee joint from 0° to 120°flexion. Methods ： Three posterior cruciate ligaments （PCL） reconstruction procedures were performed, namely two-band two-tunnel reconstruction, one-band anterior tunnel reconstruction and one-band posterior tunnel reconstruction. The posterior displacement of the tibia in relation to the femur was measured when a 200N posterior force was applied. Results： Within the flexion range of 0° to 30°, the displacement in the one-band posterior tunnel reconstruction showed little difference from that of an intact knee （P〉0.05）. But when the flexion exceeded 30°, especially when it exceeded 60°, the displacement in oneband posterior tunnel reconstruction was much greater than that of an intact knee （P〈0.01）. In two-band two-tunnel reconstruction and one-band anterior tunnel reconstruction, the displacement was approximately the same as that of an intact knee ranging from 0° to 120° （P〉0.05）, while a slight over-restriction might be found at some angles. Conclusions： Two-band reconstruction could effectively restrict the posterior displacement of the tibia and restore anterior, posterior stability of the knee joint within its full range of flexion. One-band anterior tunnel reconstruction also could maintain the posterior stability of the knee, while the result of one-band posterior tunnel reconstruction is the most unsatisfactory.
