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| In [[condensed matter physics]], the '''resonating valence bond theory''' (RVB) is a [[theoretical physics|theoretical model]] that attempts to describe [[high temperature superconductivity]], and in particular the superconductivity in [[cuprate]] compounds. It was first proposed by [[People of the United States|American]] physicist [[P. W. Anderson]] and the Indian theoretical physicist [[Ganapathy Baskaran]] in 1987.<ref name=nature-2011>{{cite journal|last=Mann|first=Adam|title=High-temperature superconductivity at 25: Still in suspense|journal=Nature|year=2011|volume=475|pages=280–282|doi=10.1038/475280a|url=http://www.nature.com/news/2011/110720/full/475280a.html#B4|accessdate=8 April 2012|bibcode = 2011Natur.475..280M|pmid=21776057}}</ref> The theory states that in [[cuprate|copper oxide]] lattices, electrons from neighboring copper atoms interact to form a [[valence bond]], which locks them in place. However, with [[Doping (semiconductor)|doping]], these electrons can act as mobile [[Cooper pairs]] and are able to superconduct. Anderson observed in his 1987 paper that the origins of superconductivity in doped cuprates was in the [[Mott insulator]] nature of crystalline copper oxide.<ref name=arxiv-history>{{cite journal|last=Zaanen|first=Jan|title=A modern, but way too short history of the theory of superconductivity at a high temperature|journal=ArXiv|year=2010|url=http://arxiv.org/abs/1012.5461}} [arXiv:1012.5461v2]</ref> RVB builds on the [[Hubbard model|Hubbard]] and [[t-J model]]s used in the study of [[strongly correlated material]]s.<ref name=weber-2007>{{cite book|last=Weber|first=Cédric|title=Variational Study of Strongly Correlated Electron Models|year=2007|publisher=École Polytechnique Fédérale de Lausanne|url=http://www.tcm.phy.cam.ac.uk/~cw489/Cedric_homepage/Welcome_files/these.pdf}}</ref>
| | My name is Trudy and I am studying Agriculture and Life Sciences and Economics at Sittard / Netherlands.<br><br>my homepage - [http://Www.Tubextc.com/video/Ahryan_Astyn_Sucking_Cock-29033/ hdporn] |
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| ==Description==
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| [[File:Valence bond solid.png|thumb|right|The RVB state with [[valence bond]] coupling of nearest-neighbor electrons.]]
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| The physics of Mott insulators is described by the repulsive Hubbard model [[Hamiltonian (quantum mechanics)|Hamiltonian]]:
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| <math>H=-t\sum_{\langle ij\rangle}c^{\dagger}_{i\sigma}c_{j\sigma}+\text{h.c.}+U\sum_in_{i\uparrow}n_{i\downarrow}</math>
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| In 1971, Anderson first suggested that this Hamiltonian can have a non-degenerate ground state that is composed of disordered spin states. Shortly after the high-temperature superconductors were discovered, Anderson and Kivelson et al. proposed a ''resonating valence bond'' ground state for these materials, written as
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| <math>|\text{RVB}\rangle=\sum_C|C\rangle</math>
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| Where <math>C</math> represented a covering of a lattice by nearest neighbor dimers. Each such covering is weighted equally. In a [[mean field approximation]], the RVB state can be written in terms of a [[Gutzwiller projection]], and displays a superconducting phase transition per the [[Kosterlitz-Thouless]] mechanism.<ref name=baskaran2009>{{cite journal|last=Baskaran|first=Ganapathy|title=Five-fold way to new high Tc superconductors|journal=Pramana|year=2009|volume=73|issue=1|pages=61–112|doi=10.1007/s12043-009-0094-8|url=http://www.ias.ac.in/pubs/splpubs/pjubileebook/279.pdf|accessdate=8 April 2012|bibcode = 2009Prama..73...61B }}</ref> However, a rigorous proof for the existence of a superconducting ground state in either the Hubbard or the t-J Hamiltonian is not yet known.<ref name=baskaran2009 /> Further the stability of the RVB ground state has not yet been confirmed.<ref name=kotliar1989>{{cite journal|last=Dombre|first=Thierry|coauthors=Gabriel Kotliar|title=Instability of the long-range resonating valence bond state in the mean-field approach|journal=Physical Review B|year=1989|volume=39|issue=1|pages=855–857|url=http://www.physics.rutgers.edu/~kotliar/papers/PRB_39_855.pdf|accessdate=8 April 2012|bibcode = 1989PhRvB..39..855D |doi = 10.1103/PhysRevB.39.855 }}</ref>
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| ==References==
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| {{reflist|1}}
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| [[Category:High-temperature superconductors]]
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| [[Category:Condensed matter physics]]
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| [[Category:Theoretical physics]]
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Latest revision as of 04:16, 13 January 2015
My name is Trudy and I am studying Agriculture and Life Sciences and Economics at Sittard / Netherlands.
my homepage - hdporn