Unusual NMR signatures of superconductivity in the two-dimensional quasicrystal ( Ta 0.95 Cu 0.05 ) 1.6 Te

Physical properties in the normal and superconducting (SC) state are investigated with $^{125}\mathrm{Te}$-nuclear magnetic resonance (NMR) measurements in a quasicrystal ${({\mathrm{Ta}}_{0.95}{\mathrm{Cu}}_{0.05})}_{1.6}\mathrm{Te}$, which was a recently discovered superconductor with the SC transition temperature ${T}_{\mathrm{c}}=0.94 \mathrm{K}$. The nuclear spin-lattice relaxation rate $1/{T}_{1}$ shows a coherence peak just below ${T}_{\mathrm{c}}$, followed by an exponential decrease down to 0.1 K. The overall temperature dependence of $1/{T}_{1}$ is in good agreement with an $s$-wave SC model with an SC gap slightly smaller than the BCS value. However, the coherence peak is unusually small, which may be attributable to a reduced Bogoliubov peak theoretically predicted for quasicrystals. Furthermore, $^{125}\mathrm{Te}\text{\ensuremath{-}}\mathrm{NMR}$ spectra show marginal shift and almost no linewidth broadening below ${T}_{\mathrm{c}}$, revealing unusual superconducting responses in this quasicrystal.