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تسجيل مستخدم جديدComparison of charge modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and YBa$_2$Cu$_3$O$_{6.6}$
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A charge modulation has recently been reported in (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ [Ghiringhelli {em et al.} Science 337, 821 (2013)]. Here we report Cu $L_3$ edge soft x-ray scattering studies comparing the lattice modulation associated with the charge modulation in YBa$_2$Cu$_3$O$_{6.6}$ with that associated with the well known charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$. We find that the correlation length in the CuO$_2$ plane is isotropic in both cases, and is $259 pm 9$ AA for La$_{1.875}$Ba$_{0.125}$CuO$_4$ and $55 pm 15$ AA for YBa$_2$Cu$_3$O$_{6.6}$. Assuming weak inter-planar correlations of the charge ordering in both compounds, we conclude that the order parameters of the lattice modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and YBa$_2$Cu$_3$O$_{6.6}$ are of the same order of magnitude.
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The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that
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We report combined soft and hard x-ray scattering studies of the electronic and lattice modulations associated with stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$. We find that the amplitude of both the el
ectronic modulation of the hole density and the strain modulation of the lattice is significantly larger in La$_{1.875}$Ba$_{0.125}$CuO$_4$ than in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ and is also better correlated. The in-plane correlation lengths are isotropic in each case; for La$_{1.875}$Ba$_{0.125}$CuO$_4$, $xi^{hole}=255pm 5$ AA whereas for La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$F, $xi^{hole}=111pm 7$ AA. We find that the modulations are temperature independent in La$_{1.875}$Ba$_{0.125}$CuO$_4$ in the low temperature tetragonal phase. In contrast, in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$, the amplitude grows smoothly from zero, beginning 13 K below the LTT phase transition. We speculate that the reduced average tilt angle in La$_{1.875}$Ba$_{0.125}$CuO$_4$ results in reduced charge localization and incoherent pinning, leading to the longer correlation length and enhanced periodic modulation amplitude.
Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge a
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