1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT...1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT;superconductivity in the Institute ofPhysics, Academia Sinica. A few monthslater we not only confirmed the展开更多
Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density...Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density in the Al phase and γa characteristic parameter. Decrease of Tc in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. γand Tc,maxin equation (*) stands for the influence of the electron-phonon interaction and n2for the influence of the electron-electron Coulomb repulsion on Tc. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al1−x(SiO2)x cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al1−x(SiO2)x cermets between different phases.展开更多
The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational ...The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.展开更多
The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, si...The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, sintering temperature, sintering time, and compacted pressure. The XRD-pattern exhibited a tetragonal phase for both Cu-1223, and Cu-1212. The resistivity measurement was considered the important experiment to show the predominant phase of superconductor if it was a high phase or low phase. The critical temperature (Tc) was about (128 K) for the high phase of Cu-1223, whereas the low phase of (Cu-1212) appeared at (Tc = 64 K). The correlation between the Miller indices and resistivity measurements was a good tool to predicate the expected mechanism of conductivity within the unit cell. It was clear that the arrangement of these planes was aligned in the a-c direction. That should make the motion of the charge to be simpler by a stepping plane toward c-axis.展开更多
High Tc Superconductors （HTS） have special electromagnetic characteristics and phenomena. Effort has been made in order to theoretically understand the appfied HTS superconductivity and HTS behaviors for practical a...High Tc Superconductors （HTS） have special electromagnetic characteristics and phenomena. Effort has been made in order to theoretically understand the appfied HTS superconductivity and HTS behaviors for practical appfications, various theoretical models related to the HTS electromagnetic properties have been developed. The theoretical models and analytic methods are summarized with regard to understanding the HTS magnetic flux characteristic which is one of the most critical issues related to HTS appfications such as for HTS magnetic levitation application.展开更多
Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is...Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is not very great,but their magnetic behaviours are different from each other.The magnetization loops of these compounds have been measured at 77K.The coexistence of superconductivity with magnetic ordering (COSM) found in the samples with RE=Gd,Dy,Ho,Er,Tm,indicates that there are two possible ways of coexistence in the samples.These expertments show that the relation of paramagnetism to the atomtc number of rare earth elements for these superconductors is similar to that of rare earth ions in some paramagnetic salt crystals,which indicates that the magnetism of the samples origi- nates from the local magnetic moments of rare earth ions.In some samples there is antiferromagnetie ordering at low temperatures,and the effective Bohr magneton numbers are consistent with that of free rare earth ions. Some superconducting parameters including the critical current density are calculated according to Ginzburg-Landau theory and the critical state model.展开更多
Various optical luminescence spectroscopic techniques were used to characterize the high T_c superconductor YBa_2Cu_3O_x.The emission bands reveal that Cu^(3+) coexist with Cu^(2+) and Cu^+ in this material.
The pursuit of designing superconductors with high Tc has been a long-standing endeavor.However,the widespread incorporation of doping in high Tc superconductors significantly impacts electronic structure,intricately ...The pursuit of designing superconductors with high Tc has been a long-standing endeavor.However,the widespread incorporation of doping in high Tc superconductors significantly impacts electronic structure,intricately influencing Tc.The complex interplay between the structural composition and material performance presents a formidable challenge in superconductor design.Based on a novel generative model,diffusion model,and doping adap-tive representation:three-channel matrix,we have designed a high Tc super-conductors inverse design model called Supercon-Diffusion.It has achieved remarkable success in accurately generating chemical formulas for doped high Tc superconductors.Supercon-Diffusion is capable of generating superconduc-tors that exhibit high Tc and excels at identifying the optimal doping ratios that yield the peak Tc.The doping effectiveness(55%)and electrical neutrality(55%)of the generated doped superconductors exceed those of traditional GAN models by more than tenfold.Density of state calculations on the structures further confirm the validity of the generated superconductors.Additionally,we have proposed 200 potential high Tc superconductors that have not been documented yet.This groundbreaking contribution effectively reduces the search space for high Tc superconductors.Moreover,it successfully establishes a bridge between the interrelated aspects of composition,structure,and prop-erty in superconductors,providing a novel solution for designing other doped materials.展开更多
The increase of the critical temperature Tc for superconductivity in Al1−x(SiO2)x cermets with increasing x correlates with a decrease of the electron density n due to electron transfer, expressed by Tc/Tc,max=1−γ⋅n2...The increase of the critical temperature Tc for superconductivity in Al1−x(SiO2)x cermets with increasing x correlates with a decrease of the electron density n due to electron transfer, expressed by Tc/Tc,max=1−γ⋅n2(*). Behind the formula (*) and Tc/Tc,max=1−82.6(P−0.16)2, which is characteristic of hole-doped cuprat high-temperature superconductors, lies a general phenomenon, namely electron transfer, which equalizes potential differences in the material and leads to a strong reduction of n. P is the fraction of holes filled by the transferred electrons. A quantitative consideration gives Tc(x)/Tc,max=1−(1−x1−x0)2(**), where x is the doping concentration and x0 is the concentration at which superconductivity begins. At x=xmax=1the electron source is completely depleted and with further growth of x the hole density p starts to increase and Tc decreases until superconductivity disappears completely at x=2−x0. Taking into account the formula (**), the hypothesis arose that for x>xmaxTc/Tc,max=1−γ⋅p2(***), an analogue of the formula (*), and that superconductivity is possible not only by electron-Cooper pairs but also by paired holes. The mechanisms described here for HTSC suggest an analogy to the physics of semiconductors and that of nanocomposites: Electron-hole duality. The “P=1/8” anomaly in YBa2Cu3O6+x is caused by the simultaneous presence of electrons and holes, a consequence of incomplete electron transfer.展开更多
Strong current and large-scale application is the most important prospect of high Te superconductors （HTS）. Practical HTS samples in various forms have been produced with high critical currents operated at economic ...Strong current and large-scale application is the most important prospect of high Te superconductors （HTS）. Practical HTS samples in various forms have been produced with high critical currents operated at economic cryogenic temperatures. Engineering applications of those HTS materials have been studied with various HTS prototype devices. The applicable HTS materials produced in different forms are verified in this paper with regard to their strong current characterizations, and the HTS applications are summarized along with the HTS prototypes made.展开更多
文摘1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT;superconductivity in the Institute ofPhysics, Academia Sinica. A few monthslater we not only confirmed the
文摘Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density in the Al phase and γa characteristic parameter. Decrease of Tc in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. γand Tc,maxin equation (*) stands for the influence of the electron-phonon interaction and n2for the influence of the electron-electron Coulomb repulsion on Tc. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al1−x(SiO2)x cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al1−x(SiO2)x cermets between different phases.
文摘The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.
文摘The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, sintering temperature, sintering time, and compacted pressure. The XRD-pattern exhibited a tetragonal phase for both Cu-1223, and Cu-1212. The resistivity measurement was considered the important experiment to show the predominant phase of superconductor if it was a high phase or low phase. The critical temperature (Tc) was about (128 K) for the high phase of Cu-1223, whereas the low phase of (Cu-1212) appeared at (Tc = 64 K). The correlation between the Miller indices and resistivity measurements was a good tool to predicate the expected mechanism of conductivity within the unit cell. It was clear that the arrangement of these planes was aligned in the a-c direction. That should make the motion of the charge to be simpler by a stepping plane toward c-axis.
文摘High Tc Superconductors （HTS） have special electromagnetic characteristics and phenomena. Effort has been made in order to theoretically understand the appfied HTS superconductivity and HTS behaviors for practical appfications, various theoretical models related to the HTS electromagnetic properties have been developed. The theoretical models and analytic methods are summarized with regard to understanding the HTS magnetic flux characteristic which is one of the most critical issues related to HTS appfications such as for HTS magnetic levitation application.
基金Supported by the Chinese National Science Foundation and originally published in J.Chin.RE Soc.(Chin.ed.),1989,7(2),63.
文摘Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is not very great,but their magnetic behaviours are different from each other.The magnetization loops of these compounds have been measured at 77K.The coexistence of superconductivity with magnetic ordering (COSM) found in the samples with RE=Gd,Dy,Ho,Er,Tm,indicates that there are two possible ways of coexistence in the samples.These expertments show that the relation of paramagnetism to the atomtc number of rare earth elements for these superconductors is similar to that of rare earth ions in some paramagnetic salt crystals,which indicates that the magnetism of the samples origi- nates from the local magnetic moments of rare earth ions.In some samples there is antiferromagnetie ordering at low temperatures,and the effective Bohr magneton numbers are consistent with that of free rare earth ions. Some superconducting parameters including the critical current density are calculated according to Ginzburg-Landau theory and the critical state model.
文摘Various optical luminescence spectroscopic techniques were used to characterize the high T_c superconductor YBa_2Cu_3O_x.The emission bands reveal that Cu^(3+) coexist with Cu^(2+) and Cu^+ in this material.
基金support from the fund of Science and Technology on Reactor Fuel and Materials Laboratory(JCKYS2019201074)the Guangdong Basic and Applied Basic Research Foundation(2022A1515110676)+4 种基金the Shenzhen Science and Technology Program(JCYJ20220531095404009,RCBS20221008093057027,JCYJ20230807094313028,JCYJ20230807094318038)the Natural Science Foundation of China(Grant No.62102118)the Project of Educational Commission of Guangdong Province of China(Grant No.2021KQNCX274)the Shenzhen Colleges and Universities Stable Support Program(Grant No.GXWD20220811170504001)the Project Supported by Sunrise(Xiamen)Photovoltaic Industry Co.,Ltd.(Development of Artificial Intelligence Technology for Perovskite Photovoltaic Materials,No.HX20230176).
文摘The pursuit of designing superconductors with high Tc has been a long-standing endeavor.However,the widespread incorporation of doping in high Tc superconductors significantly impacts electronic structure,intricately influencing Tc.The complex interplay between the structural composition and material performance presents a formidable challenge in superconductor design.Based on a novel generative model,diffusion model,and doping adap-tive representation:three-channel matrix,we have designed a high Tc super-conductors inverse design model called Supercon-Diffusion.It has achieved remarkable success in accurately generating chemical formulas for doped high Tc superconductors.Supercon-Diffusion is capable of generating superconduc-tors that exhibit high Tc and excels at identifying the optimal doping ratios that yield the peak Tc.The doping effectiveness(55%)and electrical neutrality(55%)of the generated doped superconductors exceed those of traditional GAN models by more than tenfold.Density of state calculations on the structures further confirm the validity of the generated superconductors.Additionally,we have proposed 200 potential high Tc superconductors that have not been documented yet.This groundbreaking contribution effectively reduces the search space for high Tc superconductors.Moreover,it successfully establishes a bridge between the interrelated aspects of composition,structure,and prop-erty in superconductors,providing a novel solution for designing other doped materials.
文摘The increase of the critical temperature Tc for superconductivity in Al1−x(SiO2)x cermets with increasing x correlates with a decrease of the electron density n due to electron transfer, expressed by Tc/Tc,max=1−γ⋅n2(*). Behind the formula (*) and Tc/Tc,max=1−82.6(P−0.16)2, which is characteristic of hole-doped cuprat high-temperature superconductors, lies a general phenomenon, namely electron transfer, which equalizes potential differences in the material and leads to a strong reduction of n. P is the fraction of holes filled by the transferred electrons. A quantitative consideration gives Tc(x)/Tc,max=1−(1−x1−x0)2(**), where x is the doping concentration and x0 is the concentration at which superconductivity begins. At x=xmax=1the electron source is completely depleted and with further growth of x the hole density p starts to increase and Tc decreases until superconductivity disappears completely at x=2−x0. Taking into account the formula (**), the hypothesis arose that for x>xmaxTc/Tc,max=1−γ⋅p2(***), an analogue of the formula (*), and that superconductivity is possible not only by electron-Cooper pairs but also by paired holes. The mechanisms described here for HTSC suggest an analogy to the physics of semiconductors and that of nanocomposites: Electron-hole duality. The “P=1/8” anomaly in YBa2Cu3O6+x is caused by the simultaneous presence of electrons and holes, a consequence of incomplete electron transfer.
文摘Strong current and large-scale application is the most important prospect of high Te superconductors （HTS）. Practical HTS samples in various forms have been produced with high critical currents operated at economic cryogenic temperatures. Engineering applications of those HTS materials have been studied with various HTS prototype devices. The applicable HTS materials produced in different forms are verified in this paper with regard to their strong current characterizations, and the HTS applications are summarized along with the HTS prototypes made.
