中国物理B ›› 2024, Vol. 33 ›› Issue (2): 27401-027401.doi: 10.1088/1674-1056/ad03dc

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Disorder effects in NbTiN superconducting resonators

Wei-Tao Lyu(吕伟涛)1, Qiang Zhi(支强)1, Jie Hu(胡洁)2, Jing Li(李婧)1, and Sheng-Cai Shi(史生才)1,†   

  1. 1 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210034, China;
    2 GEPI, Observatoire de Paris, PSL Université, CNRS, Paris 75014, France
  • 收稿日期:2023-07-30 修回日期:2023-10-13 接受日期:2023-10-17 出版日期:2024-01-16 发布日期:2024-01-16
  • 通讯作者: Sheng-Cai Shi E-mail:scshi@pmo.ac.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11925304 and 12020101002) and the Chinese Academy of Sciences Program (Grant No. GJJSTD20210002).

Disorder effects in NbTiN superconducting resonators

Wei-Tao Lyu(吕伟涛)1, Qiang Zhi(支强)1, Jie Hu(胡洁)2, Jing Li(李婧)1, and Sheng-Cai Shi(史生才)1,†   

  1. 1 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210034, China;
    2 GEPI, Observatoire de Paris, PSL Université, CNRS, Paris 75014, France
  • Received:2023-07-30 Revised:2023-10-13 Accepted:2023-10-17 Online:2024-01-16 Published:2024-01-16
  • Contact: Sheng-Cai Shi E-mail:scshi@pmo.ac.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11925304 and 12020101002) and the Chinese Academy of Sciences Program (Grant No. GJJSTD20210002).

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摘要： Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap ($\varDelta$), critical temperature ($T_{\rm c}$), and quasiparticle density of states (QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro-phonon coupling, can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the $\varDelta $, $T_{\rm c}$, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide (CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter $\alpha $ and the critical temperature in the pure state $T_{\rm c}^{\rm P}$ of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

关键词: effects of disorder, NbTiN, superconducting film, Usadel equation, complex conductivity, superconducting resonator

Abstract: Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap ($\varDelta$), critical temperature ($T_{\rm c}$), and quasiparticle density of states (QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro-phonon coupling, can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the $\varDelta $, $T_{\rm c}$, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide (CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter $\alpha $ and the critical temperature in the pure state $T_{\rm c}^{\rm P}$ of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

Key words: effects of disorder, NbTiN, superconducting film, Usadel equation, complex conductivity, superconducting resonator

中图分类号:  (Effects of disorder)

  • 74.62.En
74.78.-w (Superconducting films and low-dimensional structures) 85.25.Pb (Superconducting infrared, submillimeter and millimeter wave detectors) 74.25.nn (Surface impedance)