$^{93}$Nb NMR investigation of vortex- glass transition in layered NbSe$_{2}$

We report a detailed low temperature investigation of vortex glass transition in layered superconducting compound NbSe$_{2}$ using $^{93}$Nb NMR at fields below H$_{c2}$. Preliminary measurements show that spin-lattice relaxation rate 1/$T_{1}$ demonstrates a classic Korringa behavior 1/$T_{1\, }$\textasciitilde $T$ above the superconducting transition $T_{c}$ , consistent with previous measurements on this compound. However, for field $H$ perpendicular to the layers, we observed that 1/$T_{1}$ exhibits an anomalous plateau between $T_{c}$ ($H=$0) and $T_{c}(H)$ and a suppression of the superconducting enhancement expected below $T_{c}$. Instead, a power law behavior, 1/$T_{1}$ \textasciitilde $T^{1.2}$ below $T_{c}$ down to 360mK was observed which suggests a strong anisotropy in the low energy excitations. However, the possibility of enhancement in 1/$T_{1}$ due to vortex fluctuations which competes with electronic mechanisms cannot be excluded. The implications of these results with regards to vortex-glass transition will be discussed.