Phase Diagrams of a 2D Dilute Antiferromagnetic Ising Model with Charged Impurities
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In this work, we address a topical problem of a competition of charge and spin ordering for high-T cuprates. We have studied a simplified static 2D spin-pseudospin model on a square lattice, which takes into account both conventional antiferromagnetic spin exchange coupling and the on-site and intersite charge correlations in the CuO2 planes with the on-site Hilbert space reduced to only three effective valent states. We compared an analytical results for the ground state and for the temperature phase diagrams obtained in a mean field approximation and a large amount of the classical Monte Carlo calculations. Numerical results show that homogeneous ground state antiferromagnetic solutions found in a mean field approximation are unstable for the “strong” exchange limit with respect to phase separation with the charge and spin subsystems behaving like immiscible quantum liquids. We found an analytical expression for critical temperature of phase separation and performed the comparison with the Monte Carlo results.
KeywordsCuprates Spin and charge ordering Mean field
The authors thank Konrad Kapcia for fruitful discussion.
The work was supported by Act 211 Government of the Russian Federation, agreement No 02.A03.21.0006, and by the Ministry of Education and Science, projects 2277 and 5719.