Signatures of the electronic nature of pairing in high-Tc superconductors obtained by non-equilibrium boson spectroscopy

As is shown, thermally assisted vortex motion can come into being in high-T c superconductors due to the applied temperature gradient. Its behavior strongly depends on the local and global microstructure of the samples, moreover on the temperature and magnetic field. Investigation of the density, size and intensity of the pinning centers of specimens leads to the conclusion that the higher homogeneity immediately weakens and the lower one strenghtens the pinning, thus the former promotes and the latter impedes the vortex motion. The non-equilibrium experimental technique together with a.c. susceptibility measurements render possible the direct determination of the velocity of vortices. Depending on the actual microstructural state of samples it has the values between 6 × 10-2 mm/s and 18 × 10-2 mm/s in the case of Y-Ba-Cu-O specimens investigated.

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NON-EQUILIBRIUM RADIATION RESPONSE AND DECOUPLING OF VORTEX-ANTIVORTES PAIRS IN TWO-DIMENSIONAL HIGH-Tc SUPERCONDUCTORS

Acta Physica Sinica ◽

10.7498/aps.49.989 ◽

2000 ◽

Vol 49 (5) ◽

pp. 989

Author(s):

XU KE-XI

Keyword(s):

Radiation Response ◽

Two Dimensional ◽

High Tc Superconductors ◽

High Tc ◽

Equilibrium Radiation ◽

Non Equilibrium

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The many faces of STEM in materials science

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086507 ◽

1991 ◽

Vol 49 ◽

pp. 440-441

Author(s):

John Silcox

Keyword(s):

Materials Science ◽

Auger Spectroscopy ◽

Dark Field ◽

High Tc Superconductors ◽

High Tc ◽

Acoustic Environment ◽

Electromagnetic Vibration ◽

The Many ◽

Serial Mode

Determination of the microstructure and microchemistry of small features often provides the insight needed for the understanding of processes in real materials. In many cases, it is not adequate to use microscopy alone. Microdiffraction and microspectroscopic information such as EELS, X-ray microprobe analysis and Auger spectroscopy can all contribute vital parts of the picture. For a number of reasons, dedicated STEM offers considerable promise as a quantitative instrument. In this paper, we review progress towards effective quantitative use of STEM with illustrations drawn from studies of high Tc superconductors, compound semiconductors and metallization of H-terminated silicon.Intrinsically, STEM is a quantitative instrument. Images are acquired directly by detectors in serial mode which is particularly convenient for digital image acquisition, control and display. The VG HB501A at Cornell has been installed in a particularly stable electromagnetic, vibration and acoustic environment. Care has been paid to achieving UHV conditions (i.e., 10-10 Torr). Finally, it has been interfaced with a VAX 3200 work station by Kirkland. This permits, for example, the acquisition of bright field (or energy loss) images and dark field images simultaneously as quantitative arrays in perfect registration.

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Crystal chemistry of high-Tc superconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178720 ◽

1990 ◽

Vol 48 (4) ◽

pp. 1118-1119

Author(s):

Maryvonne Hervieu

Keyword(s):

Oxygen Deficiency ◽

Large Family ◽

Copper Oxides ◽

High Tc Superconductors ◽

High Tc ◽

Single Mechanism ◽

Square Planar ◽

History Of ◽

Bismuth Cuprates ◽

New Compounds

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.

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