There are increasing indications that superconductivity competes with other orders in cuprate superconductors, but obtaining direct evidence with bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations with an incommensurate periodicity of ∼3.2 lattice units in the copper-oxide planes of the superconductors (Y,Nd)Ba2Cu3O6+x with hole concentrations 0.09≤p≤0.13 per planar Cu ion. The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature, Tc; further cooling below Tc abruptly reverses the divergence of the charge correlations. In combination with prior observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge-density-wave instability that competes with superconductivity.
@article{arxiv.1207.0915,
title = {Long-range incommensurate charge fluctuations in (Y,Nd)Ba2Cu3O(6+x)},
author = {G. Ghiringhelli and M. Le Tacon and M. Minola and S. Blanco-Canosa and C. Mazzoli and N. B. Brookes and G. M. De Luca and A. Frano and D. G. Hawthorn and F. He and T. Loew and M. Moretti Sala and D. C. Peets and M. Salluzzo and E. Schierle and R. Sutarto and G. A. Sawatzky and E. Weschke and B. Keimer and L. Braicovich},
journal= {arXiv preprint arXiv:1207.0915},
year = {2015}
}