发表机构
Old Dominion University（老道明大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究人员从Eliashberg理论计算极端第二类超导体的超热场，发现其超热场与热力学磁场的比值高于弱耦合BCS模型，且Nb₃Sn的超热场在特定散射参数下存在最大值。
AI 中文摘要
我们从各向同性Eliashberg理论计算具有大Ginzburg-Landau参数的第二类超导体的超热场$H_s$。结果表明，对于不同的散射参数$p=\frac{\bar{h}}{2πτ_Nk_BT_c}$，可通过热力学方法在非磁性杂质散射时间$τ_N$的宽范围（从干净极限$p\ll1$到脏极限$p\gg1$）内得到$H_s(T)$的温度依赖关系。利用从隧道测量提取的电子-声子谱函数，对Nb和Nb₃Sn进行了具体计算。我们发现，由Eliashberg理论计算的比值$H_s(T,p)/H_c(T)$（其中$H_c$为热力学磁场）超过了弱耦合BCS模型的对应比值。还表明，尽管非磁性杂质在载流态下是对破坏体，但Nb₃Sn在$T=0$时的$H_s(0,p)$在$p\u22480.2$处存在一个最大值，此时$H_s/H_c$的比值比BCS干净极限下的比值高约6%。
英文摘要
We calculate the superheating field $H_s$ of a type-II superconductor with a large Ginzburg-Landau parameter from the isotropic Eliashberg theory. It is shown that the temperature dependencies of $H_s(T)$ can be obtained from a thermodynamic approach for different scattering parameters $p=\hbar/2πτ_Nk_BT_c$ in a wide range of the nonmagnetic impurity scattering times $τ_N$ ranging from the clean $(p\ll 1)$ to the dirty $(p\gg 1)$ limits. Specific calculations were done for Nb and Nb$_3$Sn using their electron-phonon spectral functions extracted from tunneling measurements. We show that the ratio $H_s(T,p)/H_c(T)$ calculated from the Eliashberg theory exceeds that of the weak coupling BCS model, where $H_c$ is the thermodynamic magnetic field. We also show that, even though nonmagnetic impurities are pairbreakers in the current-carrying state, $H_s(0,p)$ for Nb$_3$Sn at $T=0$ has a maximum at $p\approx 0.2$ at which the ratio $H_s/H_c$ is about $6\%$ higher than that in the BCS clean limit.
