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Title: Electronic Structure Theory
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High Temperature Superconductivity in Cuprates


Zhang-Rice Singlet


Zhang-Rice Singlet in Na0.03Ca1.97CuO2Cl2
Spin density of Na0.03Ca1.97CuO2 (red/blue = up/down). The Cu ion in the centre (Grey spheres) is surrounded by four O ions (red spheres) with a net down spin which indicates that a hole, introduced by replacing one Ca by an Na has localised on those ions to form a state known as a Zhang-Rice singlet.

The discovery of high temperature superconductivity in cuprates is now 20 years old. The search for a detailed explanation of superconductivity in these materials continues. An interesting feature of many doped cuprates is that their CuO2 planes, which are believed to carry the supercurrent, have a superlattice structure commonly known as 'stripes'. In Na0.125Ca1.875CuO2Cl2 a 4x4 superlattice has been observed by STM by the Davis group at Cornell University. Our hybrid density functional calculations lead us to believe that stripes may be a phenomenon whereby holes localise on O ions in CuO2 planes in a similar fashion to hole localisation to form Zener polarons in MnO2 planes in manganites. Using a B3LYP hybrid density functional method we find that a single hole doped into a 4x4 supercell localises around one Cu ion (see figure on left) to form a Zhang-Rice singlet configuration

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Last updated: Mar 21 2012.

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