Abstract
A well-isolated Zhang-Rice (ZR) singlet as a ground state of the Cu center in hole-doped cuprates is a leading paradigm in modern theories of high-temperature superconductivity. However, a dramatic temperature evolution of the Li NMR signal in LaLiCuO, a system with a regular lattice of well-isolated Cu 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 and orbitals rather than a conventional Cu 3-O 2 hybrid. The temperature variation of the Li 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 K. This behavior agrees with a stripelike ferrodistortive fluctuating order in a two-dimensional structure of the (CuLi)O planes accompanied by unconventional oxygen orbital antiferromagnetic fluctuations.
- Received 1 August 2012
DOI:https://doi.org/10.1103/PhysRevB.86.241107
©2012 American Physical Society