High-resolution Angle-resolved Photoemission Studies of High Tc Superconductor Bi Sub 2 Sr Sub 2 CaCu Sub 2 O Sub 8

High-resolution Angle-resolved Photoemission Studies of High Tc Superconductor Bi Sub 2 Sr Sub 2 CaCu Sub 2 O Sub 8
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Total Pages: 71
Release: 1990
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An angle-resolved photoemission study of the normal and superconducting states in Bi2Sr2CaCu2O was performed. Measurements in the normal state show bands dispersing through the Fermi level from at least 350 meV below E{sub F}. The Fermi level crossings are consistant with local-density band calculation, including a point calculated to be of Bi-O character. Additional measurements were made where bands crossed the Fermi level between 100 and 250K, along with measurements on an adjacent Pt foil. The Fermi edges of both materials agree to within the noise. Below the Fermi level, the spectra show correlation effects on the form of an increased effective mass. The shape of the spectra can be explained by a lifetime-broadened photohole and secondary electrons. The effective inverse photohole lifetime is linear in energy. A superconducting gap has been measured at a number of points where there is density at the Fermi level in the normal state. By proper modeling, a gap of 24 meV was obtained for all these points, including points of Cu-O and Bi-O character respectively, according to band calculation. The lack of gap anisotropy in the basal plane suggests that pinning in this material is not d-wave pairing.

Photoemission Spectroscopy on High Temperature Superconductor

Photoemission Spectroscopy on High Temperature Superconductor
Author: Wentao Zhang
Publisher: Springer Science & Business Media
Total Pages: 147
Release: 2012-08-22
Genre: Technology & Engineering
ISBN: 364232472X

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This book mainly focuses on the study of the high-temperature superconductor Bi2Sr2CaCu2O8 by vacuum, ultra-violet, laser-based, angle-resolved photoemission spectroscopy (ARPES). A new form of electron coupling has been identified in Bi2212, which occurs in the superconducting state. For the first time, the Bogoliubov quasiparticle dispersion with a clear band back-bending has been observed with two peaks in the momentum distribution curve in the superconducting state at a low temperature. Readers will find useful information about the technique of angle-resolved photoemission and the study of high-temperature superconductors using this technique. Dr. Wentao Zhang received his PhD from the Institute of Physics at the Chinese Academy of Sciences.

Angle-Resolved Photoemission Spectroscopy on High-Temperature Superconductors

Angle-Resolved Photoemission Spectroscopy on High-Temperature Superconductors
Author: Junfeng He
Publisher: Springer
Total Pages: 137
Release: 2016-06-21
Genre: Technology & Engineering
ISBN: 3662527324

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This book mainly focuses on the study of the high-temperature superconductor Bi2Sr2CaCu2O8+δ (Bi2212) and single-layer FeSe film grown on SrTiO3 (STO) substrate by means of angle-resolved photoemission spectroscopy (ARPES). It provides the first electronic evidence for the origin of the anomalous high-temperature superconductivity in single-layer FeSe grown on SrTiO3 substrate. Two coexisted sharp-mode couplings have been identified in superconducting Bi2212. The first ARPES study on single-layer FeSe/STO films has provided key insights into the electronic origin of superconductivity in this system. A phase diagram and electronic indication of high Tc and insulator to superconductor crossover have been established in the single-layer FeSe/STO films. Readers will find essential information on the techniques used and interesting physical phenomena observed by ARPES.

Spectral Weight Changes at the Superconducting Transition of Bi Sub 2 Sr Sub 2 CaCu Sub 2 O Sub 8+. Delta

Spectral Weight Changes at the Superconducting Transition of Bi Sub 2 Sr Sub 2 CaCu Sub 2 O Sub 8+. Delta
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Total Pages: 11
Release: 1991
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An overview of our gap studies in high-{Tc} superconductors is presented for the workshop on Fermiology of high-{Tc}'s. The work is centered on the study of single crystal Bi2Sr2CaCu2O{sub 8+{delta}}. In a conventional BCS superconductor, a superconducting gap [Delta] is formed when the near Fermi edge electrons condense to form Cooper pairs at low temperatures. As the material goes superconducting the density of states is modified such that the spectral intensity in the region from the Fermi energy down to an energy [Delta] is transferred to a regions just below [Delta]. While this spectral weight transfer has in the past been studied with tunneling spectroscopy, the size of the gap as well as improvements in our instrument resolution allow us now to study it with photoelectron spectroscopy. We have found that as the sample goes superconducting, not only is there spectral weight transfer from the gap region as in BCS theory, but along the [Gamma]-M direction there is also some spectral weight transfer from higher binding energies resulting in a dspectral dip at about -90 meV relative E{sub F}. The total spectral weight decreases along the [Gamma]-M direction, but actually increases along the [Gamma]-X direction. This temperature dependent spectral transfer is discussed in terms of (1) a two to three dimensional phase transition from RVB theory; (2) a manifestation of the electron-boson interaction in the form of [alpha]2F oscillations; and (3) conformity with the theory of Van Hove singularities. The latter are particularly attractive in that there are several other observations possibly explained by them: (1) the observation that the magnitude of the gap is anisotropic in the a-b plane; (2) the observation that for overdoped samples the magnitude of D appears to fall off faster then {Tc}. 25 refs., 8 figs., 1 tab.