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Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La2CuO4

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2014
Author Haefliger P. S., Gerber S., Pramod R., Schnells V. I., dalla Piazza B., Chati R., Pomjakushin V., Conder K., Pomjakushina E., Le Dreau L., Christensen N. B., Syljuasen O. F., Normand B., Ronnow H. M.,
Project Mott Physics Beyond the Heisenberg Model in Iridates and Related Materials
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Original article (peer-reviewed)

Journal PHYSICAL REVIEW B
Volume (Issue) 89(8)
Page(s) 085113
Title of proceedings PHYSICAL REVIEW B
DOI 10.1103/PhysRevB.89.085113

Open Access

URL http://infoscience.epfl.ch/record/198023?ln=en
Type of Open Access Repository (Green Open Access)

Abstract

We study the zero-point and thermal ionic motion in La2CuO4 by means of high-resolution neutron-diffraction experiments. Our results demonstrate anisotropic motion of O and, to a lesser extent, Cu ions, both consistent with the structure of coupled CuO6 octahedra, and quantify the relative effects of zero-point and thermal contributions to ionic motion. By substitution of O-18, 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.
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