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

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Title Direct evidence of non-Zhang-Rice Cu3+ centers in La2Li0.5Cu0.5O4
 
Creator MOSKVIN, AS
GIPPIUS, AA
TKACHEV, AV
MAHAJAN, AV
CHAKRABARTY, T
PRESNIAKOV, IA
SOBOLEV, AV
DEMAZEAU, G
 
Subject MAGNETIC EXCITATIONS
LA2CU0.5LI0.5O4
COPPER
STATE
SUPERCONDUCTORS
LA2CU1-XLIXO4
SINGLET
OXIDES
PHASES
 
Description 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 Li-6,Li-7 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 a(2g)(pi) and e(u)(pi) orbitals rather than a conventional b(1g)(d(x2-y2))Cu 3d-O 2p hybrid. The temperature variation of the Li-6,Li-7 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)O-2 planes accompanied by unconventional oxygen orbital antiferromagnetic fluctuations. DOI: 10.1103/PhysRevB.86.241107
 
Publisher AMER PHYSICAL SOC
 
Date 2014-10-15T15:21:55Z
2014-10-15T15:21:55Z
2012
 
Type Article
 
Identifier PHYSICAL REVIEW B, 86(24)
http://dx.doi.org/10.1103/PhysRevB.86.241107
http://dspace.library.iitb.ac.in/jspui/handle/100/15140
 
Language en