Electronic states and molecular dynamics of single-component molecular conductors [M(tmdt)${}_2$] (M=Ni, Pt) studied by ${}^{13}$C and ${}^1$H NMR

The molecular conductors [M(tmdt)${}_2$] (M=Ni, Pt) consisting of single molecular species are investigated with ${}^{13}$C NMR and ${}^1$H NMR. The temperature dependences of ${}^{13}$C NMR shift and relaxation rate provide microscopic evidences for the metallic nature with appreciable electron correlations. Both compounds exhibit an anomalous frequency-dependent enhancement in ${}^1$H nuclear spin-lattice relaxation rate in a wide temperature range. These observations signify the presence of extraordinary molecular motions with low energy excitations.