超导射频腔表面耗散的三流体模型
A Three-Fluid Model of Dissipation at Surfaces in Superconducting Radiofrequency Cavities
浏览论文内容
中文总结 AI 辅助
该研究针对超导射频腔的反Q斜率问题，通过数值求解Bogoliubov-de Gennes方程，提出三流体模型并结合半经典理论，揭示了表面与连续谱准粒子态的相对散射率对反Q斜率的调控机制。
中文摘要 AI 辅助
超导腔实验发现，在大射频场下品质因数会随场振幅增大而提升，即所谓的“反Q斜率”。我们在平行磁场下的超导表面数值求解Bogoliubov-de Gennes方程，发现大场下存在体超导能隙以下的表面准粒子态，会随磁场周期出现和消失。我们修改标准双流体模型，引入“三流体模型”，将正常流体拆分为连续谱和表面准粒子态分别考虑。我们在半经典电导率理论中计算耗散，其中从体铌中杂质的互补ab initio计算得到类点杂质的势强度，据此给出Bogoliubov准粒子弹性散射时间的物理估计。我们在这一简单却有效的框架中表明，表面与连续谱准粒子态的相对散射率如何在产生反Q斜率中发挥作用，同时展示该模型如何自然包含开启和关闭反Q斜率的机制。
英文摘要
Experiments on superconducting cavities have found that under large RF fields the quality factor can improve with increasing field amplitude, a so-called ``anti-Q slope.'' We numerically solve the Bogoliubov-de Gennes equations at a superconducting surface in a parallel magnetic field, finding at large fields there are surface quasiparticle states with energies below the bulk superconducting gap that emerge and disappear as the field cycles. Modifying the standard two-fluid model, we introduce a ``three''-fluid model where we partition the normal fluid to consider continuum and surface quasiparticle states separately. We compute dissipation in a semi-classical theory of conductivity, where we provide physical estimates of elastic scattering times of Bogoliubov quasiparticles with point-like impurities having potential strengths informed from complementary \textit{ab initio} calculations of impurities in bulk niobium. We show, in this simple yet effective framework, how the relative scattering rates of surface and continuum quasiparticle states can play a role in producing an anti-Q slope while demonstrating how this model naturally includes a mechanism for turning the anti-Q slope on and off.
