Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La${}_2$CuO${}_4$

Abstract

We study the zero-point and thermal ionic motion in La${}_2$CuO${}_4$ by means of high-resolution neutron diffraction experiments. Our results demonstrate anisotropic motion of O and to a lesser extent of Cu ions, both consistent with the structure of coupled CuO${}_6$ octahedra, and quantify the relative effects of zero-point and thermal contributions to ionic motion. By substitution of ${}^{18}$O, we find that the oxygen isotope effect on the lattice dimensions is small and negative ($-0.01\%$), while the isotope effect on the ionic displacement parameters is significant ($-6$ to $50\%$). We use our results as input for theoretical estimates of the distribution of magnetic interaction parameters, $J$, in an effective one-band model for the cuprate plane. We find that ionic motion causes only small ($1\%$) effects on the average value $⟨J⟩$, which vary with temperature and O isotope, but results in dramatic ($10$-$20\%$) fluctuations in $J$ values that are subject to significant ($8$-$12\%$) isotope effects. We demonstrate that this motional broadening of $J$ can have substantial effects on certain electronic and magnetic properties in cuprates.

13 pages, 9 figures

References in corpus (6)

• Inelastic Light Scattering From Correlated Electrons
• Anomalous High-Energy Spin Excitations in La2CuO4
• Quantum dynamics and entanglement of spins on a square lattice
• Using the average spectrum method to extract dynamics from quantum Monte Carlo simulations
• The Two-Dimensional Square-Lattice S=1/2 Antiferromagnet Cu(pz)${}_2$(ClO${}_4$)${}_2$
• Lifetime of Gapped Excitations in a Collinear Quantum Antiferromagnet

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• Strain-Engineering Mott-Insulating La${}_2$CuO${}_4$
• Similar temperature scale for valence changes in Kondo lattices with different Kondo temperatures
• Thermal conductivity in large-$J$ two-dimensional antiferromagnets: Role of phonon scattering
• Heat Transport in Spin Chains with Weak Spin-Phonon Coupling
• Hybridization and Decay of Magnetic Excitations in two-dimensional Triangular Lattice Antiferromagnets
• Negative Oxygen Isotope Effect on the Static Spin Stripe Order in La_(2-x)Ba_xCuO_4 (x = 1/8)
• Oxygen Isotope Effects on Lattice Properties of La_{2-x}Ba_xCuO_4 (x = 1/8)
• Electronic structure, doping, order and disorder in cuprate superconductors