NMR and Vortex Lattice Melting in YB${\mathrm{a}}_2$C${\mathrm{u}}_3$${\mathrm{O}}_7$

We report ${}^{89}$Y and ${}^{17}$O NMR (9 T) echo decays for YB${\mathrm{a}}_2$C${\mathrm{u}}_3$ ${\mathrm{O}}_7$ and correct for contributions from dipolar coupling ${}^{63,65}$Cu in order to isolate effects of vortex dynamics. We confirm vortex localization in the solid state with rms displacements consistent with Langevin dynamical theory, but with motional dynamics at time scales $(10–100\mu \mathrm{s})$ some $\sim {10}^6$ times slower than predicted. Vortex migration over longer time scales is restricted to distances less than 1/100 of an intervortex spacing over times as long as 100 ms, in contrast with the rapid long range diffusion occurring in the liquid state.