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Strong Coupling Descriptions of High Temperature Superconductors: Electronic Attraction from a Repulsive Potential

W. Barford·M. W. Long
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Abstract

We consider the effect of the nearest neighbour copper-oxygen repulsion, V, when coupled to the charge transfer resonances Cu2+ to Cu3+ and Cu2+ to Cu+ in the high temperature cuprate superconductors. This is done by deriving effective low energy Hamiltonians correct to second order in the copper-oxygen hybridisation. Only hole doping is considered. When Cu2+ to Cu3+ fluctuations dominate we derive an effective one-band model of `Zhang-Rice' singlets with a nearest neighbour repulsion between these singlets. When Cu2+ to Cu+ fluctuations dominate we find rich and complex behaviour. For large V we show that clusters of charge are more stable than isolated charges. On the other hand, for small V the Hamiltonian contains both weak attractive and repulsive two body potentials. Calculations on clusters indicate that the attractive potentials have the same correlations as the more dominate `single particle' terms suggesting the possibility of `s' wave pairing.

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W. Barford, M. W. Long. 1994-07-13. Strong Coupling Descriptions of High Temperature Superconductors: Electronic Attraction from a Repulsive Potential. https://doi.org/10.1088/0953-8984%2F5%2F2%2F008

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