Title: Signatures of Enhanced Superconducting Properties in Niobium Cavities Show Chinese title

Title: 铌腔中超导性质增强的特征

Abstract: Superconducting radio-frequency (SRF) niobium cavities are critical for modern particle accelerators, as well as for advancing superconducting quantum systems and enabling ultra-sensitive searches for new physics. In this work, we report a systematic observation of an anomalous frequency dip in Nb cavities, which occurs at temperatures just below the critical temperature ($T_\mathrm{c}$), indicative of enhanced superconducting properties at $T \ll T_c$. The magnitude of this dip is strongly correlated with the RF surface resistance, impurity distribution near the surface, and $T_\mathrm{c}$. We also present the first demonstration of the coherence peak in the AC conductivity of Nb SRF cavities. By comparing recent theories developed to model this experimental data, we show that the frequency dip feature, larger coherence peak height, and reduction in the temperature-dependent surface resistance with RF current occur at minimal but finite levels of disorder. Show Chinese abstract

Abstract: 超导射频（SRF）铌腔对于现代粒子加速器至关重要，同时对于发展超导量子系统以及实现对新物理的超高灵敏度搜索也具有重要意义。 在这项工作中，我们报告了在铌腔中观察到的一种异常频率下降现象的系统性研究，这种现象发生在接近临界温度（$T_\mathrm{c}$）的温度下，表明在$T \ll T_c$处超导性能增强。 这一下降幅度与射频表面电阻、表面附近的杂质分布以及$T_\mathrm{c}$强烈相关。 我们还展示了铌SRF腔体交流电导率中相干峰的第一个演示。 通过比较最近开发用于模拟这些实验数据的理论模型，我们发现频率下降特征、更高的相干峰高度以及随射频电流变化的温度依赖性表面电阻在最小但有限的无序状态下出现。