Susceptibility measurements on Bi_(2)Sr_(2)CaCu_(2)O_(8) single crystals do reveal field-induced-suppression of sharp phase transition.No apparent anisotropy of the susceptibility was observed when magnetic field was ...Susceptibility measurements on Bi_(2)Sr_(2)CaCu_(2)O_(8) single crystals do reveal field-induced-suppression of sharp phase transition.No apparent anisotropy of the susceptibility was observed when magnetic field was applied along the three main directions a,b and c.The three dimensional isotropic fluctuation diamagnetism theory is proposed to explain our experimental finding of isotropic susceptibility.In a wide range of magnetic field,the temperature dependence of susceptibility does not show any obvious change in its character when the sample enters into expected vortex-lattice state from vortex-liquid state.展开更多
Samples of Bi_(2.2)Sr_(1.8)Ca_(1.05)Cu_(2.15-x)Na_(x)O_(8+y)(x=0,0.7)were prepared by melt-processing technique.The maximum transition temperature increased up to 100 K,and T_(c)0 achieved 92.5K.In order to study the ...Samples of Bi_(2.2)Sr_(1.8)Ca_(1.05)Cu_(2.15-x)Na_(x)O_(8+y)(x=0,0.7)were prepared by melt-processing technique.The maximum transition temperature increased up to 100 K,and T_(c)0 achieved 92.5K.In order to study the mechanism of T_(c) increasing,samples were annealed in a flowing oxygen,atmosphere.The reversibility of T_(c) was observed in undoped sample,while the T_(c) of Na-doped sample had no significant changes.We believe that the T_(c) is correlated with a redistribution of holes between the BiO layers and the CuO planes.Doping sodium changes the hole density of CuO planes into an“optimium”value so as to increase T_(c).展开更多
We study,via Dean's method and scattering transfer-matrix approach,the acoustic waves of one-dimensional structure with correlated disorder,which is realized by randomly inserting impurity segments into a pure hos...We study,via Dean's method and scattering transfer-matrix approach,the acoustic waves of one-dimensional structure with correlated disorder,which is realized by randomly inserting impurity segments into a pure host chain.There exist completely reflectionless acoustic modes,whose number is less than the number of atoms in a segment by 1.The frequencies of these modes are situated in the smooth parts of the phonon spectrum.We present the curves of transmission of incident waves versus frequencies,which show sharp resonant peaks at the reflectionless modes.The possible applications of this property are discussed.展开更多
基金Supported by the National Center for Research and Development on SuperconductivityInstitute of Crystal Material of Shandong University.
文摘Susceptibility measurements on Bi_(2)Sr_(2)CaCu_(2)O_(8) single crystals do reveal field-induced-suppression of sharp phase transition.No apparent anisotropy of the susceptibility was observed when magnetic field was applied along the three main directions a,b and c.The three dimensional isotropic fluctuation diamagnetism theory is proposed to explain our experimental finding of isotropic susceptibility.In a wide range of magnetic field,the temperature dependence of susceptibility does not show any obvious change in its character when the sample enters into expected vortex-lattice state from vortex-liquid state.
基金the National Center for Research and Development on Superconductivitythe National Doctoral Education and Center of Material Analysis of Nanjing University.
文摘Samples of Bi_(2.2)Sr_(1.8)Ca_(1.05)Cu_(2.15-x)Na_(x)O_(8+y)(x=0,0.7)were prepared by melt-processing technique.The maximum transition temperature increased up to 100 K,and T_(c)0 achieved 92.5K.In order to study the mechanism of T_(c) increasing,samples were annealed in a flowing oxygen,atmosphere.The reversibility of T_(c) was observed in undoped sample,while the T_(c) of Na-doped sample had no significant changes.We believe that the T_(c) is correlated with a redistribution of holes between the BiO layers and the CuO planes.Doping sodium changes the hole density of CuO planes into an“optimium”value so as to increase T_(c).
基金Supported by the National Natural Science Foundation of China。
文摘We study,via Dean's method and scattering transfer-matrix approach,the acoustic waves of one-dimensional structure with correlated disorder,which is realized by randomly inserting impurity segments into a pure host chain.There exist completely reflectionless acoustic modes,whose number is less than the number of atoms in a segment by 1.The frequencies of these modes are situated in the smooth parts of the phonon spectrum.We present the curves of transmission of incident waves versus frequencies,which show sharp resonant peaks at the reflectionless modes.The possible applications of this property are discussed.
