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| Format: | Artículo científico |
| Language: | en |
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Sociedad Mexicana de Física A.C.
2006
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| Online Access: | https://www.redalyc.org/articulo.oa?id=57065201 |
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Table of Contents:
- Optical conductivity the optical conductivity resonance from an exact description of the electronic states around the Fermi energy F. Puch R. Baquero Física, Astronomía y Matemáticas mechanism YBa2Cu3O7 resonante Superconductivity Optical Conductivity In this paper we show that the optical conductivity can be calculated to agree with experiment if the details of the electronic states around theFermi level are taken into account with some care. More precisely, we present a calculation of the optical conductivity in YBa2Cu3O7 onthe basis of an exact (ab initio) three dimensional electronic band structure calculation from which we extract the information on the bandsnear the Fermi energy that can be associated with the CuO2 plane-carrier states. To simulate the superconducting state, we superimpose agap on these bands alone. On these basis, from the known Kubo-Greenwood formula we calculate the optical conductivity in the normal andin the superconducting state. Our calculation agrees with the experimental result even in the higher part of the frequency spectrum. Our wayof calculating the resonance suggests a model of evolution for the bands under the effect of doping consistent with the recent experimentalfindings that the optical resonance can disappear while the sample remains superconducting. An important conclusion of this paper is that theresonance depends mostly on the details of the electronic band structure. It is enough to take into account the effect of the superconductingtransition through a single parameter (the gap). No details on the mechanism are needed, so no mechanism can be tested on this basis. Ourcalculation suggests a model of evolution for the bands around the Fermi energy under doping that gives some microscopic foundations tothe recent experiments that show unambiguously that the resonance cannot be the cause of superconductivity. Most importantly, it indicateshow the background is built up and depends on the electronic excitations accessible through values of the energy transfer on a wider intervalthan the one contributing directly to the resonance. These electronic excitations are determined by the optical transitions allowed. From thispoint of view, it is an obvious consequence that the background is with small differences, common to all the cuprates having a CuO2 plane.But the most important conclusion is that the background contains essentially the same physics as the resonance does, and so it does not haveany detailed information on the superconducting mechanism as well, contrary to the conclusions of recent work. 2006 artículo científico 0035-001X https://www.redalyc.org/articulo.oa?id=57065201 en http://www.redalyc.org/revista.oa?id=570 Revista Mexicana de Física application/pdf Sociedad Mexicana de Física A.C. Revista Mexicana de Física (México) Num.4 Vol.52