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一、引言 高温氧化物超导材料一出现,科学家们就注意将它制成薄膜材料、以此迈向实用化。利用高温氧化物超导材料制造超导量子干涉探测器,高速微芯片,红外探测器、高温超导晶体管等是各国科学家应用开发的重要领域,其他如超导混频器、超导天线等可用于通信、军事等领域具有广阔的前途。已经发展了许多方法制备高温超导薄膜,诸如DC或RF磁控溅射、 相似文献
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自从1986年初Bednorz和M¨uller发现镧钡铜氧化物是临界温度高于30K的超导材料以来,人们开始使用高温超导电性或常规(conventional)超导电性这些名词.开始时这样说是想强调新发现的这些铜氧化物超导材料与其他的超导材料在临界温度上有很大差异.但是随着研究工作的逐步深入,这样说的含义已远远超出当初强调临界温度的差异的意思,而变成在物理上有深刻内涵的分类了.迄今已发现的近60种铜氧化物超导材料,从它们的晶体结构、正常态和超导态的物理性质、这些性质和材料的化学组成的关系等等方面,… 相似文献
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由于对称性破缺、晶格失配、电荷转移和空间限域等多自由度的协同关联作用,氧化物异质界面演生出许多与相应体材料所不同的物理性质,其中氧化物界面超导由于蕴含丰富物理内涵吸引了广泛的关注.近年来,得益于氧化物异质外延以及物性精准表征技术的迅猛发展,研究人员已经在多种氧化物异质界面上观测到了准二维的界面超导,并研究了与其相关的许多新奇量子现象,不仅推动了凝聚态物理研究的发展,也为界面超导走向实际应用奠定了重要基础.本文主要介绍和讨论氧化物界面上的准二维超导,以典型的LaAlO3/SrTiO3界面准二维超导及La2CuO4/La1.56Sr0.44CuO4等铜氧化物界面超导为例,总结分析氧化物界面超导中新奇的物理现象,并指出该研究体系目前存在的一些问题,最后展望界面超导未来的发展方向. 相似文献
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层状材料一直是超导研究领域的热点材料, 陆续有数十种新型的层状超导材料被不断发现, 从至今为止超导转变温度最高的铜氧化物材料, 到铁基超导, 再到诸多新型的层状材料, 学者们关于超导微观机制的理解也在随之更新, 从取得成功的 Bardeen-Cooper-Schrieffer 经典理论到至今无法解释的非常规超导机制, 研究之路从未停止. 本文将研究利用助熔剂法合成的 LaO1 -xFxBiS2 材料的结构、 电阻、 磁化率等性质, 并与国际社会上已存在的研究成果进行对比, 同时从晶体结构、 压力效应、 体超导电性、 临界温度、 微观机制五个方面, 对近年发现的镧系铋硫基层状超导材料的研究情况进行讨论. 相似文献
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在Y-Ba-Cu-O系超导材料中有两个Y-Ba-Cu的氧化物,一个是超导正交相,经微区X射线能谱分析,该相钇与钡的原子比约为1:2。晶体沿c方向的超结构周期是畸变钙铁矿型亚结构的三倍。从晶体沿α方向的高分辨电子显微象可看到在钇原子周围的铜原子在c方向的距离略小于钡原子周围的铜原子间距,这是由于在垂直于c方向的钇原子层上没有氧原子,从而造成Y-Cu-O亚晶胞的畸变。另一个Y-Ba-Cu的氧化物也属正交晶系,晶胞参数α=7.12A,b=12.2A,c=5.56A。钇与钡的原子比约为2:1。在La-Ba-Cu-O化合物中,超导相有四方晶胞,晶胞大小类似于上述超导相。晶体中有大量90°晶畴,晶畴大小约百埃数量级。这是由于材料中La原子过剩,多余的La原子集中于畴界处而造成的。 相似文献
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Cl. Kriebel O. Hoffels R. Borowski H. Gottschalk H. Alexander D. Wohlleben 《Annalen der Physik》1995,507(2):136-143
A new method which allows the detection of the superconducting phase transition of high-Tc superconductors (HTSC) on a microscopic scale is reported. Micro-size holes in thin foils of superconducting material are examined in a transmission electron microscope at varying temperatures. The superconducting transition induces small changes in the image intensity within the holes, which can be detected by using electronic image analysis. Superconducting transition curves are then obtained for various types of high-Tc superconductors and for given values of the applied magnetic field. 相似文献
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57Fe Mossbauer measurement have been performed in the Fe-doped high-Tc phase of Bi-system superconductor. Isomer shifts display presence of Fe3+ ions in square and pyramidal coordinations. Regarding the high-Tc superconductors as primarily ionic crystals and using effective valence and point charge model, we have calculated the electric
field gradients for Fe as a replacement for Cu in the high-Tc phase. Good agreement between theory and experiment is obtained. 相似文献
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I. Kirschner R. Laiho A.C. Bódi E. Lähderanta M. Marosvölgyi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):283-292
Repetition of cooling and heating of high-Tc superconductors is detected to be able to result in some change of their microstructure. A non-equilibrium experimental technique
provides direct measurement of the velocity of vortex motion in high-Tc Y-Ba-Cu-O superconductors. Its value falls in the interval of mm/s depending on the number of the cooling or heating cycles, to which the samples are submitted. The thermal cycling created
homogenization of the specimen's microstructure, and is presumed to cause this phenomenon, decreasing the number and strength
of pinning centers. This supposition is proved by X-ray diffractography and transmission electron microscopy. A simple irreversible
thermodynamic theory is elaborated to describe the reason, direction and dissipative character of the vortex motion.
Received: 17 December 1997 / Accepted: 28 January 1998 相似文献
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本文探讨非晶态超导体的Tc与原子质量M之间的关系,发现在具有相同价电子数的同族元素中,超导Tc与原子质量的立方根成反比,即Tc∝l/M1/3。讨论了晶态超导体的Tc问题,其中包括高Tc氧化物超导体。
关键词: 相似文献
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Based on structural and bonding features, a new classification scheme of
superconductors is proposed to classify them into three classes: three-dimensional,
two-dimensional and molecule-assembled superconductors. The sandwich model' for the
high-Tc cuprates is extended to a `binary structure model': i.e., the
crystal structure of most superconductors can be partitioned into two parts, a
superconducting active component and a supplementary component. Partially metallic
covalent bonding is found to be a common feature in all superconducting active
components, and the electron states of the atoms in the active components usually
make a dominant contribution to the energy band near the Fermi surface. Possible
directions to explore new superconductors are discussed based on the structural
classification and the binary structure model. 相似文献
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Beginning in the late 1980s, many unexpected superconductors have emerged. They raised not only the transition temperature limit but, just as importantly, the theoretical challenges beyond the BCS theory. Following the previous article on historical perspective of low-temperature specific heat of superconductors prior to 1986, we review briefly here some calorimetric studies on representative high-Tc and other novel superconductors discovered during the new era. Major emphasis is centered on special features of each set of temperature- and magnetic field-dependent specific heat data being fitted to select theoretical models. The models may involve multi-gap or a certain type of order-parameter symmetry. 相似文献
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《Solid State Communications》1987,63(8):725-727
It is shown that the ratio β = ϵ/Tc (ϵ is the energy gap at T = OK) saturates with increasing strength of the electron-phonon interaction; the value βmax is calculated. The special case of a multigap superconductor is discussed. New high-Tc superconductors present a unique oppurtunity to observe a multigap structure. 相似文献