Zero resistance and Meissner effect are two crucial experimental evidences of superconductivity in determining a new kind of superconductor, which can be detected by transport and diamagnetic measurements. In this pap...Zero resistance and Meissner effect are two crucial experimental evidences of superconductivity in determining a new kind of superconductor, which can be detected by transport and diamagnetic measurements. In this paper, we briefly review the main transport and magnetization results on the one unit cell (1-UC) FeSe films grown on SrTiO3 (STO) substrates from our team in recent years, which identify the high temperature superconductivity in 1-UC FeSe films.展开更多
The velocity of blown sand particles is an important parameter in aeolian movement (a special case of gas particle two-phase flow) and has ever been a topic of interest. At present, several techniques have been appl...The velocity of blown sand particles is an important parameter in aeolian movement (a special case of gas particle two-phase flow) and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods: photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer (PDA) method and Particle Image Velocimetry (PIV) method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.展开更多
We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature T...We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state.Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor Ba Fe1.9 Ni0.1 As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.展开更多
It was found that selenium doping can suppress the charge-density-wave(CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point...It was found that selenium doping can suppress the charge-density-wave(CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point(QCP) in ZrTe3-xSex near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe(3-x)Sex single crystals(x = 0.044 and 0.051) down to 80 m K. For both samples, the residual linear term κ0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe(3-x)Sex,which indicates conventional superconductivity despite of the existence of a CDW QCP.展开更多
Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load tran...Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load transport rate by adopting the sedimentation pit method and resolving such key problems as weighing and desilting, which can achieve long-time, all-weather and real-time telemeasurement of the bed load transport rate of plain rivers, estuaries and coasts. Both laboratory and field tests show that this monitor is reasonable in design, stable in properties and convenient in measurement, and it can be used to monitor the bed load transport rate in practical projects.展开更多
Three spectroscopic systems have been developed for the study of light impurity particle transport in the HT-7 tokamak. A visible multi-channel spectroscopic system (VIS) is used to obtain the brightness distributio...Three spectroscopic systems have been developed for the study of light impurity particle transport in the HT-7 tokamak. A visible multi-channel spectroscopic system (VIS) is used to obtain the brightness distribution of the line emission from ionized light impurities. The profile of Zeff(r) has been obtained from the visible multi-channel bremsstrahlung measurement (VB). The system with a rotating hexahedral mirror for space-time resolved spectroscopy measurement from ultraviolet to visible (UV) can provide the brightness distribution of two different emission lines of the light impurities simultaneously. The emissivities by these multi-channel measurements can be obtained by Abel inversion. The measurement was performed in typical OH discharges in the HT-7 tokamak. The carbon particle transport was analyzed. The feasibility of these diagnostic systems for the impurity particle transport study is clearly demonstrated.展开更多
This paper deals with the optimal transportation for generalized Lagrangian L = L(x, u, t), and considers the following cost function: c(x, y) = inf x(0)=x x(1)=y u∈U∫0^1 L(x(s), u(x(s), s), s)ds, w...This paper deals with the optimal transportation for generalized Lagrangian L = L(x, u, t), and considers the following cost function: c(x, y) = inf x(0)=x x(1)=y u∈U∫0^1 L(x(s), u(x(s), s), s)ds, where U is a control set, and x satisfies the ordinary equation x(s) = f(x(s), u(x(s), s)).It is proved that under the condition that the initial measure μ0 is absolutely continuous w.r.t. the Lebesgue measure, the Monge problem has a solution, and the optimal transport map just walks along the characteristic curves of the corresponding Hamilton-Jacobi equation:Vt(t, x) + sup u∈U = 0,V(0, x) = Φ0(x).展开更多
Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extrem...Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.展开更多
Control of magnetic anisotropy in low-dimensional systems is of paramount importance in terms of their fundamental and technological perspectives.La_(0.7)Sr_(0.3)MnO_(3)(LSMO)is a ferromagnetic half-metal with a high ...Control of magnetic anisotropy in low-dimensional systems is of paramount importance in terms of their fundamental and technological perspectives.La_(0.7)Sr_(0.3)MnO_(3)(LSMO)is a ferromagnetic half-metal with a high Curie temperature and many efforts have been made to control its magnetic anisotropy.However,the relationship between the evolution of the magnetic anisotropy orientation and the electronic structure of low-dimensional LSMO still remains poorly understood.Here,the high-quality superlattices comprised of LSMO and SrMnO_(3)(SMO)layers are synthesized with a compatible structure at the atomic scale.Their magnetic anisotropy is gradually varied from planar to perpendicular by increasing the SMO thickness,and the special fourfold magnetic anisotropy is also observed at the intermediate superlattice thickness.The evolution of the magnetic anisotropy in these systems is confirmed by the electronic transport and magnetic measurements.Moreover,X-ray linear dichroism measurements and first-principles calculations reveal the interfacial orbital reconstruction with the in-plane to out-ofplane magnetic reorientation transition.Therefore,a new microscopic method for magnetic anisotropy manipulation is developed in the present study,enabling discovery of novel phenomena as well as control of the magnetic properties.展开更多
基金supported by the National Basic Research Program of China(Grant Nos.2013CB934600 and 2012CB921300)the National Natural Science Foundation of China(Grant Nos.11222434 and 11174007)the Research Fund for the Doctoral Program of Higher Education(RFDP)of China
文摘Zero resistance and Meissner effect are two crucial experimental evidences of superconductivity in determining a new kind of superconductor, which can be detected by transport and diamagnetic measurements. In this paper, we briefly review the main transport and magnetization results on the one unit cell (1-UC) FeSe films grown on SrTiO3 (STO) substrates from our team in recent years, which identify the high temperature superconductivity in 1-UC FeSe films.
基金the funding from National Science Fund for Distinguished Young Scholars of the NaturalScience Foundation of China (40225003)the Knowledge Innovation Project of the Chinese Academy of Science(KZCX3-SW-341)
文摘The velocity of blown sand particles is an important parameter in aeolian movement (a special case of gas particle two-phase flow) and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods: photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer (PDA) method and Particle Image Velocimetry (PIV) method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.
基金supported by the Key Basic Research Program of China(Grant Nos.2015CB921401 and 2016YFA0300503)the National Natural Science Foundation of China(Grant Nos.11422429 and 11421404)+2 种基金China Postdoctoral Science Foundation(Grant No.2016T90332)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,and STCSM of China(Grant No.15XD1500200)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB04040200)
文摘We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se(4/3), which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state.Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor Ba Fe1.9 Ni0.1 As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB821402 and 2015CB921401)the National Natural Science Foundation of China(Grant Nos.91421101,11422429,and 11204312)+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,China,STCSM of China(Grant No.15XD1500200)Work at Brookhaven National Laboratory was supported by the US DOE under Contract No.DESC00112704
文摘It was found that selenium doping can suppress the charge-density-wave(CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point(QCP) in ZrTe3-xSex near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe(3-x)Sex single crystals(x = 0.044 and 0.051) down to 80 m K. For both samples, the residual linear term κ0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe(3-x)Sex,which indicates conventional superconductivity despite of the existence of a CDW QCP.
基金supported by the special program to enhance the navigation capacity of the Golden Waterway funded by the Ministry of Transport of the People’s Republic of China"Research on Key Techniques to Monitor and Simulate the River Flow and Sediment Transport"(Grant No.2011-328-746-40)
文摘Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load transport rate by adopting the sedimentation pit method and resolving such key problems as weighing and desilting, which can achieve long-time, all-weather and real-time telemeasurement of the bed load transport rate of plain rivers, estuaries and coasts. Both laboratory and field tests show that this monitor is reasonable in design, stable in properties and convenient in measurement, and it can be used to monitor the bed load transport rate in practical projects.
基金the National Natural Science Foundation of China(No.10235010)
文摘Three spectroscopic systems have been developed for the study of light impurity particle transport in the HT-7 tokamak. A visible multi-channel spectroscopic system (VIS) is used to obtain the brightness distribution of the line emission from ionized light impurities. The profile of Zeff(r) has been obtained from the visible multi-channel bremsstrahlung measurement (VB). The system with a rotating hexahedral mirror for space-time resolved spectroscopy measurement from ultraviolet to visible (UV) can provide the brightness distribution of two different emission lines of the light impurities simultaneously. The emissivities by these multi-channel measurements can be obtained by Abel inversion. The measurement was performed in typical OH discharges in the HT-7 tokamak. The carbon particle transport was analyzed. The feasibility of these diagnostic systems for the impurity particle transport study is clearly demonstrated.
文摘This paper deals with the optimal transportation for generalized Lagrangian L = L(x, u, t), and considers the following cost function: c(x, y) = inf x(0)=x x(1)=y u∈U∫0^1 L(x(s), u(x(s), s), s)ds, where U is a control set, and x satisfies the ordinary equation x(s) = f(x(s), u(x(s), s)).It is proved that under the condition that the initial measure μ0 is absolutely continuous w.r.t. the Lebesgue measure, the Monge problem has a solution, and the optimal transport map just walks along the characteristic curves of the corresponding Hamilton-Jacobi equation:Vt(t, x) + sup u∈U = 0,V(0, x) = Φ0(x).
基金supported by the National Natural Science Foundation of China(11574174,11774193,11790311,11404183,11474030,21573121 and 51421002)the National Basic Research Program of China(2015CB921000)+1 种基金the President Foundation of China Academy of Engineering Physics(YZJJLX2016010)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB07030200)
文摘Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.
基金financially supported by the National Natural Science Foundation of China(51901118,51871137,12174237,and 52171183)the 1331 Engineering of Shanxi Province+1 种基金the Research Project Supported by Shanxi Scholarship Council of China(2021-093)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2020L0237)。
文摘Control of magnetic anisotropy in low-dimensional systems is of paramount importance in terms of their fundamental and technological perspectives.La_(0.7)Sr_(0.3)MnO_(3)(LSMO)is a ferromagnetic half-metal with a high Curie temperature and many efforts have been made to control its magnetic anisotropy.However,the relationship between the evolution of the magnetic anisotropy orientation and the electronic structure of low-dimensional LSMO still remains poorly understood.Here,the high-quality superlattices comprised of LSMO and SrMnO_(3)(SMO)layers are synthesized with a compatible structure at the atomic scale.Their magnetic anisotropy is gradually varied from planar to perpendicular by increasing the SMO thickness,and the special fourfold magnetic anisotropy is also observed at the intermediate superlattice thickness.The evolution of the magnetic anisotropy in these systems is confirmed by the electronic transport and magnetic measurements.Moreover,X-ray linear dichroism measurements and first-principles calculations reveal the interfacial orbital reconstruction with the in-plane to out-ofplane magnetic reorientation transition.Therefore,a new microscopic method for magnetic anisotropy manipulation is developed in the present study,enabling discovery of novel phenomena as well as control of the magnetic properties.