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SYNTHESIS AT AMBIENT PRESSURE AND SUPERCONDUCTIVITY OF Hg-DOPED TI-BASED DOUBLE [(T1, Hg)-O]-LAYERED CDPHATES 下载免费PDF全文
The Hg-doped T1-based 2201 and 2212 phase layered cuprates have been successfully syn-thesized at ambient pressure and identified by X-ray powder diffraction and electron diffraction analysis. Compared with pure T1-based 2212 phase compound, there are indications that the corresponding Hg-doped T1-based compound (T11.8Hg0.2)Ba2CaCu2Oz exhibits much higher Tc (> 132K). 相似文献
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1911年 ,卡末林·昂内斯在金属汞中发现了超导电性 .在之后的很长一段时间内 ,人们对其中的机理认识很少 .直到 195 7年 ,BCS理论的发表才为超导电性奠定了理论基础 .传统理论认为 ,在转变温度Tc 以下 ,超导库珀对的密度随温度降低而不断增加 ,形成库珀对所需的电子 -电子吸引不是瞬时的和超距的 ,而是靠晶格振动的中介 (电子吸收或发射声子 ) .BCS理论的实验验证实现于 2 0世纪 6 0年代 .俄罗斯物理学家Eliashberg以方程组的形式将电 -声子相互作用纳入BCS理论 ,并对超导体的声子谱作出预言 .之后 ,McMillan… 相似文献
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本文讨论了热处理过程对浇铸退火方法制备的 Bi-Pb-Sr-Ca-Cu-O 样品的电子输运性质和超导电性的影响.分析了发生非金属-金属(超导)转变的物理过程.指出无论是原子的无序分布,还是氧空位所引起的无规势场增强,都会导致电子局域化增强,使得样品金属性减弱和超导转变温度降低. 相似文献
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Anderson局域化不是铜氧化合物高温超导电性变化的原因 总被引:2,自引:0,他引:2
通过对高温超导体中的元素替代效应进行分析,指出无论是在 CuO_2平面的元素替代还是不在 CuO_2平面的元素替代都不能用无序引起的载流子局域化来解释超导电性的变化和正常态性质变化.认为对超导电性根本负责的是 CuO_2平面中一定浓度的 O_(2p)空穴与 Cu3d轨道未配对的 dx~2-y~2电子的某种结合状态. 相似文献
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报道了掺Zn的重电子金属CeCu6-xZnx(x=0.05,0.1,0.15,0.2,0.3)样品的非常规制备方法以及低温电阻和低温比热容的测量结果,研究Zn含量对CeCu6-xZnx低温性质的影响及其物理原因.发现低温下Kondo散射项系数c随Zn含量的加大而减小,电阻极大值温度Tmax随Zn含量的加大而降低,CeCu6-xZnx的德拜温度ΘD随Zn含量的加大而略有上升
关键词:
重费密子系统
低温比热容
低温电阻
相干散射 相似文献
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In this article, the influence of La substitution for Sr on structure and physi-cal properties of the 2201 phase is studied. First, the crystal microstructure of the Bi2.1Sr1.9-xLaxCuOy (0≤x≤1.0) is characterized by means of X-ray diffraction and electron diffraction analyses, it is discovered that in the La-doped 2201 system with increasing La content the 2201 phase undergoes tetragnoal-orthorhombic-monoclinic structural transition. With this phase transition, the modulation vector of the 2201 phase transforms from incommensurate to commensurate, and the period of the mod- ulation wave decreases. Secondly, the superconductivity of this system is analyzed systematically. The results of the resistivity measurement show that the appropriate amount of La doping can raise the superconducting transition temperature (Tc) of the 2201 phase, with x=0.2, Tc reaches as high as 25K. However the excessive doping of La (x≥0.3) leads the 2201 phase to transit from metal to insulator and the su-perconductivity disappears. The measurement of thermoelectric power (TEP) of this system shows that with increasing La content the TEP value also increases gradu-ally. But the interesting point is that the transition from positive to negative in TEP occurs for x=0.2 sample. In addition, the electronic structure and oxygen content of this system are also studied. Based on these, we analyze the relation between the microstructure, electronic structure of the La-doped 2201 phase and its superconduc-tivity, indicating that the type of element substitution with higher valence, together with the microstructural distortion induced by the substitution affects the electronic states of Cu 3d seriously, that is, changes the degree of coulomb correlation of Cu 3d electrons, thus resulting in the transition of the type of carrier of this system and the decrease of hole carrier concentration, as well as the corresponding variation of the superconductivity of La-doped 2201 phase. 相似文献
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Exploring, manipulating, and understanding new exotic quantum phenomena in condensed-matter systems have generated great interest in the scientific community. Static and time resolved optical spectroscopies after photoexcitations are important experimental tools for probing charge dynamics and quasiparticle excitations in quantum materials. In Synergetic Extreme Condition User Facility(SECUF), we shall construct magneto-infrared and terahertz measurement systems and develop a number of ultrafast femtosecond laser based systems, including intense near to mid-infrared pump terahertz probe. In this article, we shall describe several systems to be constructed and developed in the facilities, then present some examples explaining the application of magneto optics and time resolved spectroscopy techniques. 相似文献
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We report an optical spectroscopy study on intermediate valence system Yb_(1-x)Lu_xAl_3 with x = 0, 0.25, 0.5, 0.75, and 1. The Kondo temperature in the system is known to increase with increasing Lu concentration. Therefore, it is expected that the energy scale of the hybridization gap should increase with increasing Lu concentration based on the periodic Anderson model. On the contrary, we find that the spectral structure associated with the hybridization effect shifts monotonically to lower energy. Furthermore, the Lu substitution results in a substantial increase of the free carrier spectral weight and less pronounced plasma frequency reduction upon lowering temperature. We attribute the effect to the disruption of the Kondo lattice periodicity by the random substitution of Yb by Lu. The work highlights the importance of the lattice periodicity of the rare earth element for understanding the Kondo lattice phenomena. 相似文献