1305.7503 (A. M. Milinda Abeykoon et al.)

Evidence for Fluctuating Charge Stripes far above the Charge-Ordering
Transition in La$_{1.67}$ Sr$_{0.33}$ NiO$_{4}$    [PDF]

A. M. Milinda Abeykoon, Emil S. Božin, Wei-Guo Yin, Genda Gu, John P. Hill, John M. Tranquada, Simon J. L. Billinge

The temperature evolution of structural effects associated with charge (CO) and spin order (SO) in La$_{1.67}$Sr$_{0.33}$NiO$_{4}$ has been investigated using neutron powder diffraction. We report an anomalous shrinking of the $c/a$ lattice parameter ratio that correlates with $T_{\rm CO}$. The sign of this change can be explained by the change in interlayer Coulomb energy between the static stripe-ordered state and the fluctuating stripe-ordered state or the charge-disordered state. In addition, we identify a contribution to the mean-square displacements of Ni and in-plane O atoms whose width correlates quite well with the size of the pseudogap extracted from the reported optical conductivity, with a non-Debye-like component that persists below and well above $T_{\rm CO}$. We infer that dynamic charge-stripe correlations survive to $T\sim2T_{\rm CO}$

View original: http://arxiv.org/abs/1305.7503