Fully-gapped superconductivity with rotational symmetry breaking in pressurized kagome metal CsV3Sb5

作者：X. Y. Feng, Zhongxian Zhao, J. L. Luo, Y. Zhou, Jie Yang, A. F. Fang, Haitao Yang, H.-J. Gao, Rui Zhou, Guo‐qing Zheng · 发表于：Nature Communications · 年份：2025 · DOI：10.1038/s41467-025-58941-w · 被引用次数：5 · 研究领域：Advanced Condensed Matter Physics、Topological Materials and Phenomena、Rare-earth and actinide compounds

Abstract The discovery of the kagome metal CsV 3 Sb 5 has generated significant interest in its complex physical properties, particularly its superconducting behavior under different pressures, though its nature remains debated. Here, we performed low-temperature, high-pressure 121/123 Sb nuclear quadrupole resonance (NQR) measurements to explore the superconducting pairing symmetry in CsV 3 Sb 5 . At ambient pressure, we found that the spin-lattice relaxation rate 1/ T 1 exhibits a kink at T ~ 0.4 T c within the superconducting state and follows a T 3 variation as temperature further decreases. This suggests the presence of two superconducting gaps with line nodes in the smaller one. As pressure increases beyond P c ~ 1.85 GPa, where the charge-density wave phase is completely suppressed, 1/ T 1 shows no Hebel-Slichter peak just below T c , and decreases rapidly, even faster than T 5 , indicating that the gap is fully opened for pressures above P c . In this high pressure region, the angular dependence of the in-plane upper critical magnetic field H c2 breaks the C 6 rotational symmetry. We propose the s + i d pairing at P > P c which explains both the 1/ T 1 and H c2 behaviors. Our findings indicate that CsV 3 Sb 5 is an unconventional superconductor and its superconducting state is even more exotic at high pressures.