Anisotropic upper critical field in the van der Waals superconducting quasicrystal (Ta0.7Nb0.3)1.6Te
Abstract
We investigated the upper critical field of a large single grain of the Nb-substituted van der Waals layered quasicrystal (Ta0.7Nb0.3)1.6Te. The sample exhibits a sharp superconducting transition at Tc = 1.35 K, the highest value reported to date among quasicrystal superconductors. The angular dependence of the critical field exhibits a pronounced criterion dependence: the field determined using the 10% RN (RN: normal-state resistance) criterion is well described by the anisotropic Ginzburg-Landau model, whereas those determined using the 65% and 90% RN criteria exhibit Tinkham-like angular dependence characteristic of two-dimensional superconductivity. The high-field part of the resistive transition is well described by a surface-superconductivity model and exhibits a pronounced excitation-current dependence for magnetic fields close to the ab plane, supporting the presence of surface superconductivity on the quasiperiodic ab-plane surfaces. The bulk Hc2 is strongly anisotropic, with the in-plane Hc2 exceeding the weak-coupling Pauli limit by a factor of approximately 2.5. For both field orientations, Hc2(T) deviates upward from the conventional dirty-limit Werthamer-Helfand-Hohenberg prediction at low temperatures. A phenomenologically modified Ginzburg-Landau-Abrikosov-Gorkov model incorporating a spatial distribution of the electronic diffusivity substantially improves the description of Hc2(T), suggesting that spatial variations in electronic transport properties may contribute to its anomalous temperature dependence.
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BibTeX
@misc{kasai2026anisotropic,
title = {{Anisotropic upper critical field in the van der Waals superconducting quasicrystal (Ta$_0.7$Nb$_0.3$)$_1.6$Te}},
author = {Koki Kasai and Yuki Tokumoto and Taichi Terashima and Takako Konoike and Keiichi Edagawa},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.27352},
eprint = {2609.27352},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.27352},
}
RIS
TY - UNPB
TI - Anisotropic upper critical field in the van der Waals superconducting quasicrystal (Ta_0.7Nb_0.3)_1.6Te
AU - Koki Kasai
AU - Yuki Tokumoto
AU - Taichi Terashima
AU - Takako Konoike
AU - Keiichi Edagawa
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.27352
UR - https://arxiv.org/abs/2609.27352
AB - We investigated the upper critical field of a large single grain of the Nb-substituted van der Waals layered quasicrystal (Ta_0.7Nb_0.3)_1.6Te. The sample exhibits a sharp superconducting transition at T_c = 1.35 K, the highest value reported to date among quasicrystal superconductors. The angular dependence of the critical field exhibits a pronounced criterion dependence: the field determined using the 10% R_N (R_N: normal-state resistance) criterion is well described by the anisotropic Ginzburg-Landau model, whereas those determined using the 65% and 90% R_N criteria exhibit Tinkham-like angular dependence characteristic of two-dimensional superconductivity. The high-field part of the resistive transition is well described by a surface-superconductivity model and exhibits a pronounced excitation-current dependence for magnetic fields close to the ab plane, supporting the presence of surface superconductivity on the quasiperiodic ab-plane surfaces. The bulk H_c2 is strongly anisotropic, with the in-plane H_c2 exceeding the weak-coupling Pauli limit by a factor of approximately 2.5. For both field orientations, H_c2(T) deviates upward from the conventional dirty-limit Werthamer-Helfand-Hohenberg prediction at low temperatures. A phenomenologically modified Ginzburg-Landau-Abrikosov-Gorkov model incorporating a spatial distribution of the electronic diffusivity substantially improves the description of H_c2(T), suggesting that spatial variations in electronic transport properties may contribute to its anomalous temperature dependence.
ER -