Forced Entanglement vs Anisotropic Dissipation in a Vortex Line Liquid

We present evidence for forced topological entanglement of line-like vortices in the liquid regime of ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ with columnar defects. By splaying the defects within a fixed plane (in-fan) we create a $\hat{\mathbf{c}}-\mathrm{axis}$ phase coherent vortex (string) structure which correlates with anisotropic dissipation. The high-field vortex motion is “easy” in fan and “hard” across fan in crystals—a signature of forced entanglement by a small angle splay. The high-field anisotropy is surprisingly reversed in thin films, where forced entanglement is absent.