关于能隙与Kohn反常的符合问题
On the Question of Coincidence Between Energy Gaps and Kohn Anomalies
摘要：
最近，中子散射自旋回波测量提供了高分辨率的数据上的线宽$Γ({\bf q},T)$的声学声子在传统的超导体Pb和Nb的温度依赖性。[P. Aynajian等人，Science 319，1509（2008）]。在低温下，$2Δ(T)$结构的线宽与一个与低位$\hbarω_{\bf q_{KA}}$ Kohn异常相关的峰合并，表明Pb和Nb中的$2Δ(0)$和$\hbarω_{\bf q_{KA}}$之间是一致的。在这里，我们进行了一个标准的BCS计算的声子线宽检查其温度演化，并探讨如何接近$2Δ(0)/\hbarω_{\bf q_{KA}}$必须是统一的，以符合中子数据。
英文摘要：
Recently, neutron scattering spin echo measurements have provided high resolution data on the temperature dependence of the linewidth $Γ({\bf q},T)$ of acoustic phonons in conventional superconductors Pb and Nb. [P. Aynajian, et al, Science 319, 1509 (2008)]. At low temperatures the merging of the $2Δ(T)$ structure in the linewidth with a peak associated with a low lying $\hbarω_{\bf q_{KA}}$ Kohn anomaly suggested a coincidence between $2Δ(0)$ and $\hbarω_{\bf q_{KA}}$ in Pb and Nb. Here we carry out a standard BCS calculation of the phonon linewidth to examine its temperature evolution and explore how close $2Δ(0)/\hbarω_{\bf q_{KA}}$ must be to unity in order to be consistent with the neutron data.
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