Hole-doping dependence of the magnetic penetration depth and vortex core size inYBa2Cu3Oy: Evidence for stripe correlations near18hole doping

Abstract

We report on muon spin rotation measurements of the internal magnetic field distribution $n(B)$ in the vortex solid phase of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ (YBCO) single crystals, from which we have simultaneously determined the hole-doping dependences of the in-plane Ginzburg-Landau (GL) length scales in the underdoped regime. We find that ${T}_{c}$ has a sublinear dependence on $1∕{\ensuremath{\lambda}}_{ab}^{2}$, where ${\ensuremath{\lambda}}_{ab}$ is the in-plane magnetic penetration depth in the extrapolated limits $T\ensuremath{\rightarrow}0$ and $H\ensuremath{\rightarrow}0$. The power coefficient of the sublinear dependence is close to that determined in severely underdoped YBCO thin films, indicating that the same relationship between ${T}_{c}$ and the superfluid density is maintained throughout the underdoped regime. The GL coherence length ${\ensuremath{\xi}}_{ab}$ (vortex core size) is found to increase with decreasing hole-doping concentration and to exhibit a field dependence that is explained by proximity-induced superconductivity on the CuO chains. Both ${\ensuremath{\lambda}}_{ab}$ and ${\ensuremath{\xi}}_{ab}$ are enhanced near $\frac{1}{8}$ hole doping, supporting the belief by some that stripe correlations are a universal property of high-${T}_{c}$ cuprates.