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 ¹²⁵Te-nuclear magnetic resonance (NMR) measurements in a quasicrystal (Ta0.95Cu0.05)1.6Te, which was a recently discovered superconductor with the SC transition temperature Tc=0.94 K. The nuclear spin-lattice relaxation rate 1/T₁ shows a coherence peak just below Tc, followed by an exponential decrease down to 0.1 K. The overall temperature dependence of 1/T₁ 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, ¹²⁵Te-NMR spectra show marginal shift and almost no linewidth broadening below Tc, revealing unusual superconducting responses in this quasicrystal.