Abstract
To explore the doping dependence of the recently discovered charge-density-wave (CDW) order in , we present a bulk-sensitive high-energy x-ray study for several oxygen concentrations, including strongly underdoped . Combined with previous data around the so-called 1/8 doping, we show that bulk CDW order exists at least for hole concentrations () in the planes of . This implies that CDW order exists in close vicinity to the quantum critical point for spin-density-wave (SDW) order. In contrast to the pseudogap temperature , the onset temperature of CDW order decreases with underdoping to K in . Together with a weakened order parameter this suggests a competition between CDW and SDW orders. In addition, the CDW order in shows the same type of competition with superconductivity as a function of temperature and magnetic field as samples closer to . At low the CDW incommensurability continues the previously reported linear increasing trend with underdoping. In the entire doping range the in-plane correlation length of the CDW order in axis direction depends only very weakly on the hole concentration, and appears independent of the type and correlation length of the oxygen-chain order. The onset temperature of the CDW order is remarkably close to a temperature that marks the maximum of in planar NQR/NMR experiments, potentially indicating a response of the spin dynamics to the formation of the CDW. Our discussion of these findings includes a detailed comparison to the charge stripe order in .
- Received 28 May 2014
- Revised 30 July 2014
DOI:https://doi.org/10.1103/PhysRevB.90.054514
©2014 American Physical Society