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Angle-Resolved Photoemission Spectroscopy Study of Spin Fluctuations in the Cuprate Superconductors

2022-09-13 Technology & Engineering
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Release : 2022-09-13
Genre : Technology & Engineering
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Book Synopsis Angle-Resolved Photoemission Spectroscopy Study of Spin Fluctuations in the Cuprate Superconductors by : Francisco Restrepo

Download or read book Angle-Resolved Photoemission Spectroscopy Study of Spin Fluctuations in the Cuprate Superconductors written by Francisco Restrepo. This book was released on 2022-09-13. Available in PDF, EPUB and Kindle. Book excerpt: This thesis makes significant advances towards an understanding of superconductivity in the cuprate family of unconventional, high-temperature superconductors. Even though the high-temperature superconductors were discovered over 35 years ago, there is not yet a general consensus on an acceptable theory of superconductivity in these materials. One of the early proposals suggested that collective magnetic excitations of the conduction electrons could lead them to form pairs, which in turn condense to form the superconducting state at a critical temperature Tc. Quantitative calculations of Tc using experimental data were, however, not available to verify the applicability of this magnetic mechanism. In this thesis, the author constructed an angle-resolved photoemission apparatus that could provide sufficiently accurate data of the electronic excitation spectra of samples in the normal state, data which was furthermore unusually devoid of any surface contamination. The author also applied the Bethe-Salpeter method to his uncommonly pristine and precise normal state data, and was able to predict the approximate superconducting transition temperatures of different samples. This rare combination of experiment with sophisticated theoretical calculations leads to the conclusion that antiferromagnetic correlations are a viable candidate for the pairing interaction in the cuprate superconductors.

Photoemission Spectroscopy on High Temperature Superconductor

2012-08-22 Technology & Engineering
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Release : 2012-08-22
Genre : Technology & Engineering
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Book Rating : 72X/5 ( reviews)

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Book Synopsis Photoemission Spectroscopy on High Temperature Superconductor by : Wentao Zhang

Download or read book Photoemission Spectroscopy on High Temperature Superconductor written by Wentao Zhang. This book was released on 2012-08-22. Available in PDF, EPUB and Kindle. Book excerpt: 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

2016-06-21 Technology & Engineering
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Release : 2016-06-21
Genre : Technology & Engineering
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Book Rating : 324/5 ( reviews)

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Book Synopsis Angle-Resolved Photoemission Spectroscopy on High-Temperature Superconductors by : Junfeng He

Download or read book Angle-Resolved Photoemission Spectroscopy on High-Temperature Superconductors written by Junfeng He. This book was released on 2016-06-21. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Angle-resolved Photoemission Spectroscopy (ARPES) Studies of Cuprate Superconductors

2010
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Release : 2010
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Book Synopsis Angle-resolved Photoemission Spectroscopy (ARPES) Studies of Cuprate Superconductors by :

Download or read book Angle-resolved Photoemission Spectroscopy (ARPES) Studies of Cuprate Superconductors written by . This book was released on 2010. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+[delta] (Tl2201) Tc, max ~95 K and (Bi1.35Pb0.85)(Sr1.47La0.38)CuO6+[delta] (Bi2201) Tc, max 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major di erences in the band structure. First, the Fermi surface segments close to ([pi],0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+[delta] (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is consistent with a charge density wave (CDW) origin of the pseudogap, similar to STM checkerboard patterns in the pseudogap state.

Low Energy Excitations in Cuprate High Temperature Superconductors

2013
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Release : 2013
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Book Synopsis Low Energy Excitations in Cuprate High Temperature Superconductors by : Inna Vishik

Download or read book Low Energy Excitations in Cuprate High Temperature Superconductors written by Inna Vishik. This book was released on 2013. Available in PDF, EPUB and Kindle. Book excerpt: The mechanism of superconductivity in the cuprate high temperature superconductors is an enduring problem in condensed matter physics, and a detailed experimental phenomenology is a crucial starting point for microscopic understanding. Angle-resolved photoemission spectroscopy (ARPES) measures electronic structure in momentum-space. Low-energy excitations in the cuprates, including the superconducting gap, are known to be anisotropic in momentum space, so the momentum resolution afforded by ARPES is key to understanding the physics and uncovering the mechanism. In this dissertation, I present experiments which pursue the cuprate superconductivity problem from several angles: understanding electron-boson coupling which may be involved in mediating superconductivity (Chapters 6 and 7 and Appendix B), understanding the momentum-space structure of the normal state pseudogap (Chapter 5 and Appendix A), understanding how superconductivity coexists with the pseudogap and other phases (Chapters 3 and 4). Much of this work took advantage of a recent development in ARPES technology, using a UV laser as a light source, which allows experiments to be performed with superior energy and momentum resolution. These experiments highlight the wealth of information that is available in ARPES data, including dispersions, scattering rates, and spectral gaps, and they demonstrate the importance of exploring these variables comprehensively as a function of temperature, doping, and momentum.

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