Slow-Motion $^{1}H$ NMR Study of $\kappa$-(ET)$_{2}$Cu[N(CN)$_{2}$]Br*

The recent discovery of an anomalous Nernst signal in the pseudogap phase of organic superconductor $\kappa$-(ET)$_{2}$Cu[N(CN)$_{2}$]Br suggests the presence of magnetic flux vortices above T$_{c}$.\footnote{M. S. Nam et al, Nature 449, 584-587 (2007)} We report spin-locked and line-narrowed proton NMR data on the pseudogap phase of this material. These experiments are sensitive to magnetic fluctuations, and probe far slower timescales ($10^{-6}$-$10^{-3}$s) than the previously explored NMR parameter space. Other experiments\footnote{C. H. Recchia et al, Phys. Rev. Lett. 78, 3543-3546 (1997)} have suggested that vortices leave an NMR fingerprint at these low frequencies.