Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum and thermal ionic motion, oxygen isotope effect, and
  superexchange distribution in La$_2$CuO$_4$   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
$\langle J\rangle$, 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.

10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math