In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is fou...In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau （GL） functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I- V data of Strachan et al. [Phys. Rev. Left. 87（2001） 067007]. The puzzling question of the derivative plot for the I - V curves and the controversy surrounding the values of critical exponents are discussed.展开更多
It is shown that the flux motion in high-T_(c) superconductors can be well consistently analysed by a unified materials equation.The different models of U(J)so far suggested can be shown as specific forms or limits of...It is shown that the flux motion in high-T_(c) superconductors can be well consistently analysed by a unified materials equation.The different models of U(J)so far suggested can be shown as specific forms or limits of this unified materials equation.The scaling law of flux pinning derived from this equation agrees with recent experimental observations on high-Jc NdBa2Gu3O7-δsingle crystal.The amplitude dependence of ac susceptibility derived from this equation is compared with several experimental results of high-T_(c) superconductors and a general power law is found.展开更多
An orthorhombic-to-tetragonal structural transition of high Tc Ba_(2)LaCu_(3)O_(7-y) samples was observed with transmission electron microscope(TEM).Two intermediate orthorhombic structures were discovered and discuss...An orthorhombic-to-tetragonal structural transition of high Tc Ba_(2)LaCu_(3)O_(7-y) samples was observed with transmission electron microscope(TEM).Two intermediate orthorhombic structures were discovered and discussed.Thus,the Ba_(2)LaCu_(3)O_(7-y) is another member of high Tc Ba_(2)LnCu_(3)O_(7-y)(Ln=Lathanides)family with lower structural transition temperature.展开更多
A major phase in high Tc Y-Ba-Cu oxide with zero resistance at 91K and high volume fraction of diamagnetic superconductive phase has been identified by electron diffraction.It appears to be an orthorhombic twinned str...A major phase in high Tc Y-Ba-Cu oxide with zero resistance at 91K and high volume fraction of diamagnetic superconductive phase has been identified by electron diffraction.It appears to be an orthorhombic twinned structure with a=3.89Å,b=3.82Å and c=11.7lÅ.Some defects were observed by TEM.展开更多
Epitaxial metal film sandwiches of Nb-La-Nb and Nb-Ce-Nb have been prepared in an ultra high vacuum environment.In the sandwiches the La layers and Ce layers are found to be fcc La and bcc Ce,respectively,different fr...Epitaxial metal film sandwiches of Nb-La-Nb and Nb-Ce-Nb have been prepared in an ultra high vacuum environment.In the sandwiches the La layers and Ce layers are found to be fcc La and bcc Ce,respectively,different from that of bulks.The transmission electron microscope(TEM)observations indicate that La or Ce was grown with partial pseudomorphism epitaxy on bcc Nb layers.The origin of the unusual epitaxies has been discussed.展开更多
Ⅰ. INTRODUCTION Since the Cooper pair tunnelling effect was predicted in 1962 and experimentally proved in 1963, study of superconducting thin films has developed vigorously in view of the wide application potentiali...Ⅰ. INTRODUCTION Since the Cooper pair tunnelling effect was predicted in 1962 and experimentally proved in 1963, study of superconducting thin films has developed vigorously in view of the wide application potentiality of SQUIDs. So far, the superconducting thin films used in Josephson devices are pure metals and alloys with T_c≤16 K and are able to function only under costly liquid helium conditions.展开更多
Since discovery of superconductivity around 35 K in Ba-La-Cu-O systems by BednorzMüller and observation of Meissner effect by Uchida-Takaji-Kishio to determine superconducting in the systems, research for high T_...Since discovery of superconductivity around 35 K in Ba-La-Cu-O systems by BednorzMüller and observation of Meissner effect by Uchida-Takaji-Kishio to determine superconducting in the systems, research for high T_c superconductors of such展开更多
基金Supported by the National Key Basic Research Special Foundation of China under Grant No G1999064602, and the Natlonal Natural Science Foundation of China under Grant Nos 10174003, 50377040 and 90303008.
文摘In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau （GL） functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I- V data of Strachan et al. [Phys. Rev. Left. 87（2001） 067007]. The puzzling question of the derivative plot for the I - V curves and the controversy surrounding the values of critical exponents are discussed.
基金Supported by the National Key Basic Research Special Foundation of China under Grant No G1999064602, and the National Natural Science Foundation of China under Grant No 10674005.
基金Supported by the National Natural Sciences Foundation of China under Grant No.19571006the National Center for Research and Development on Superconductivity of China.
文摘It is shown that the flux motion in high-T_(c) superconductors can be well consistently analysed by a unified materials equation.The different models of U(J)so far suggested can be shown as specific forms or limits of this unified materials equation.The scaling law of flux pinning derived from this equation agrees with recent experimental observations on high-Jc NdBa2Gu3O7-δsingle crystal.The amplitude dependence of ac susceptibility derived from this equation is compared with several experimental results of high-T_(c) superconductors and a general power law is found.
文摘An orthorhombic-to-tetragonal structural transition of high Tc Ba_(2)LaCu_(3)O_(7-y) samples was observed with transmission electron microscope(TEM).Two intermediate orthorhombic structures were discovered and discussed.Thus,the Ba_(2)LaCu_(3)O_(7-y) is another member of high Tc Ba_(2)LnCu_(3)O_(7-y)(Ln=Lathanides)family with lower structural transition temperature.
文摘A major phase in high Tc Y-Ba-Cu oxide with zero resistance at 91K and high volume fraction of diamagnetic superconductive phase has been identified by electron diffraction.It appears to be an orthorhombic twinned structure with a=3.89Å,b=3.82Å and c=11.7lÅ.Some defects were observed by TEM.
文摘Epitaxial metal film sandwiches of Nb-La-Nb and Nb-Ce-Nb have been prepared in an ultra high vacuum environment.In the sandwiches the La layers and Ce layers are found to be fcc La and bcc Ce,respectively,different from that of bulks.The transmission electron microscope(TEM)observations indicate that La or Ce was grown with partial pseudomorphism epitaxy on bcc Nb layers.The origin of the unusual epitaxies has been discussed.
文摘Ⅰ. INTRODUCTION Since the Cooper pair tunnelling effect was predicted in 1962 and experimentally proved in 1963, study of superconducting thin films has developed vigorously in view of the wide application potentiality of SQUIDs. So far, the superconducting thin films used in Josephson devices are pure metals and alloys with T_c≤16 K and are able to function only under costly liquid helium conditions.
文摘Since discovery of superconductivity around 35 K in Ba-La-Cu-O systems by BednorzMüller and observation of Meissner effect by Uchida-Takaji-Kishio to determine superconducting in the systems, research for high T_c superconductors of such
