arXiv subjects

K. Edagawa

Publications and source records attributed to K. Edagawa.

2 recordsLinked to original sources

arXiv2025

Thermodynamic evidence for full-gap superconductivity in the dodecagonal quasicrystal Cu-doped Ta$_{1.6}$Te

We report the superconducting gap in the van der Waals layered quasicrystal Cu-doped Ta$_{1.6}$Te, using a fast relaxation technique that removes the large nuclear contribution of $^{181}$Ta. The initial-slope method enabled detection of the electronic specific heat down to 60~mK, revealing a fully gapped state with $\Delta(0)/k_{\rm B} = 1.43$~K. Both the gap magnitude and specific-heat jump are smaller than BCS predictions, while quasiparticle excitations are strongly suppressed, consistent with a theoretical expectation for aperiodic systems. AC-susceptibility measurements show a large upper critical field and pronounced anisotropy, reflecting the quasi-two-dimensional structure. These results provide the first thermodynamic evidence for a full-gap superconducting state in a quasicrystal and highlight unconventional pairing mechanisms beyond periodic lattices.

cond-mat.supr-con↗

arXiv2025

Superconducting Properties on Two-dimensional Quasicrystal (Ta$_{0.95}$Cu$_{0.05}$)$_{1.6}$Te Studied with $^{125}$Te-NMR

Physical properties in the normal and superconducting (SC) state are investigated with $^{125}$Te-nuclear magnetic resonance (NMR) measurements in a quasicrystal $\mathrm{(Ta_{0.95}Cu_{0.05})_{1.6}Te}$, which was a recently discovered superconductor with the SC transition temperature $T_{\mathrm{c}}$ = 0.94 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 a 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, $^{125}$Te-NMR spectra show almost no broadening nor shift in the SC state, suggesting that an unusual SC state such as parity mixing might be realized in the Ta$_{1.6}$Te superconductor.

cond-mat.supr-con↗