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Direct evidence of non-Zhang-Rice Cu3+ centers in La2Li0.5Cu0.5O4

A. S. Moskvin, A. A. Gippius, A. V. Tkachev, A. V. Mahajan, T. Chakrabarty, I. A. Presniakov, A. V. Sobolev, and G. Demazeau
Phys. Rev. B 86, 241107(R) – Published 17 December 2012

Abstract

A well-isolated Zhang-Rice (ZR) singlet as a ground state of the Cu3+ center in hole-doped cuprates is a leading paradigm in modern theories of high-temperature superconductivity. However, a dramatic temperature evolution of the 6,7Li NMR signal in La2Li0.5Cu0.5O4, a system with a regular lattice of well-isolated Cu3+ centers, reveals significant magnetic fluctuations and suggests a quasidegeneracy to be a generic property of their ground state at variance with the simple ZR model. We argue for a competition of the ZR state with nearby states formed by a “doped” hole occupying purely oxygen nonbonding a2g(π) and eu(π) orbitals rather than a conventional b1g(dx2y2) Cu 3d-O 2p hybrid. The temperature variation of the 6,7Li NMR line shape and spin-lattice relaxation rate point to a gradual slowing down of some magnetic order parameter's fluctuations without distinct signatures of a phase transition down to T=2 K. This behavior agrees with a stripelike ferrodistortive fluctuating Ammm order in a two-dimensional structure of the (CuLi)O2 planes accompanied by unconventional oxygen orbital antiferromagnetic fluctuations.

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  • Received 1 August 2012

DOI:https://doi.org/10.1103/PhysRevB.86.241107

©2012 American Physical Society

Authors & Affiliations

A. S. Moskvin1, A. A. Gippius2, A. V. Tkachev2, A. V. Mahajan3, T. Chakrabarty3, I. A. Presniakov4, A. V. Sobolev4, and G. Demazeau5

  • 1Department of Theoretical Physics, Ural Federal University, Ekaterinburg 620083, Russia
  • 2Low Temperature Physics and Superconductivity Department, Moscow State University, Moscow 119991, Russia
  • 3Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076, India
  • 4Department of Chemistry, Moscow State University, Moscow 119991, Russia
  • 5ICMCB, CNRS, University Bordeaux 1 “Sciences and Technologies,” site de l’ENSCPB-87, Avenue du Dr. A. Schweitzer, 33608 Pessac Cedex, France

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Issue

Vol. 86, Iss. 24 — 15 December 2012

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