## Abstract

The ordered alloy (Formula presented)(Formula presented)(Formula presented)(Formula presented) is found to be a band insulator in local density approximation (LDA) calculations with the unoccupied conduction band having predominantly (Formula presented) symmetry and substantial weight in O 2p orbitals. This is equivalent to a predominant local singlet configuration (Formula presented)L or a low-spin (Formula presented) ion with both holes in orbits having (Formula presented) symmetry, i.e., Zhang-Rice singlets. A fairly modest reduction of the apical Cu-O bond length is sufficient to stabilize a high spin triplet (Formula presented) ionic configuration with holes in both (Formula presented) and (Formula presented) orbits in LDA + U calculations. This leads us to identify the low energy triplet excitation found in nuclear quadrupole resonance studies by Yoshinari et al. as a local high-spin (Formula presented) ionic configuration accompanied by a substantial reduction of the apical Cu-O separation, i.e., an anti-Jahn-Teller triplet polaron.

Original language | English |
---|---|

Pages (from-to) | 12829-12832 |

Number of pages | 4 |

Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 55 |

Issue number | 19 |

DOIs | |

Publication status | Published - 1997 |

Externally published | Yes |