$^{1}$H NMR Spin-Lattice Relaxation Study of $\kappa$-(ET)$_{2}$Cu[N(CN)$_{2}$]Br

The discovery of an anomalous Nernst signal in the organic superconductor $\kappa$-(ET)$_{2}$Cu[N(CN)$_{2}$]Br suggests the presence of magnetic flux vortices above T$_{c}^{[1]}$. Previous studies below the transition temperature have shown that the additional fluctuating field created by vortices dramatically increases the $^{1}$H NMR spin-lattice relaxation rate$^{[2]}$. We revisit $^{1}$H spin-lattice relaxation in $\kappa$-(ET)$_{2}$Cu[N(CN)$_{2}$]Br and provide new evidence of inhomogeneous behavior both above and below $T_{c}$. $^{[1]}$M. S. Nam et al, Nature 449, 584-587 (2007) $^{[2]}$H. Mayaffre et al, Phys. Rev. Lett. 76, 4951-4954 (1996) Work at UIUC supported by NSF DMR 10-05708 and the Center for Emergent Superconductivity, USDOE Award No. DE-AC0298CH1088. Work at Argonne supported by UChicago Argonne, LLC, Operator of Argonne National Laboratory, DOE Contract No. DE-AC02-06CH11357.