Experimental evidence that zinc impurities pin pair-density-wave order in La2−xBaxCuO4

Both Zn doping and $c$-axis magnetic fields have been observed to increase the spin stripe order in ${\mathrm{La}}_{2\text{\ensuremath{-}}x}{\mathrm{Ba}}_x{\mathrm{CuO}}₄$ with $x$ close to 1/8. For $x=0.095$, the applied magnetic field also causes superconducting layers to decouple, presumably by favoring pair-density-wave order that consequently frustrates interlayer Josephson coupling. Here we show that introducing 1% Zn also leads to an initial onset of two-dimensional (2D) superconductivity, followed by 3D superconductivity at lower temperatures, even in zero field. We infer that the Zn pins pair-density-wave order locally, establishing the generality of such behavior.