发表机构
School of Physics & Astronomy, University of Nottingham（诺丁汉大学物理与天文学学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过测量Pb(111)在超导转变前后的力-距离曲线和场发射谱，发现静电屏蔽变化小于1%，证实Thomas-Fermi屏蔽在超导转变中保持不变，否定了Hirsch理论。
AI 中文摘要
经验性的伦敦方程对超导体的纵向和横向电动力学响应做出了不同的预测。传统上，该框架将迈斯纳效应归因于横向分量，而纵向响应预计在进入超导态时保持不变，即静电场在Thomas-Fermi长度（$\lambda_{\mathrm{TF}} \sim 1$~Å）上被屏蔽，与正常金属中的情况相同。J.~E.~Hirsch~[\textit{Phys.~Rev.~B}~\textbf{69},~214515~(2004)]提出了另一种形式体系，预测当系统冷却到超导转变温度（$T_{\mathrm{c}}$）以下时，纵向屏蔽长度应由伦敦穿透深度决定。这里，我们结合qPlus原子力显微镜和扫描隧道显微镜/谱学，在约~340~mK~\mbox{（$T/T_{\mathrm{c}}\sim0.05$）下对单晶Pb(111)进行研究，试图探测进入超导相时纵向针尖电场静电屏蔽的任何变化。我们使用垂直于Pb(111)表面的200 mT磁场来抑制超导性。通过在有无磁场的相同样品位置测量力-距离曲线和局域场发射共振谱，我们将正常态和超导态之间屏蔽的变化限制在小于约~1\\%。这比Hirsch理论预测的值小两到三个数量级，并且与超导转变过程中Thomas-Fermi屏蔽不变完全一致。
英文摘要
The empirical London equations make distinct predictions for a superconductor's longitudinal and transverse electrodynamic response. Conventionally, this framework attributes the Meissner effect to the transverse component, with the longitudinal response predicted to remain unchanged on entering the superconducting state, i.e. a static electric field is screened over the Thomas-Fermi length ($λ_{\mathrm{TF}} \sim 1$~Å), just as in the nonsupercondcuting metal. J.~E.~Hirsch~[\textit{Phys.~ Rev.~B}~\textbf{69},~214515~(2004)] has developed an alternative formalism, which predicts that the longitudinal screening length should instead be governed by the London penetration depth as the system is cooled below the superconducting transition temperature ($T_{\mathrm{c}}$). Here we use a combination of qPlus atomic force microscopy and scanning tunneling microscopy/spectroscopy of single-crystal Pb(111) at $\sim$~340~mK~ \mbox{($T/T_{\mathrm{c}}\sim0.05$)} in an attempt to detect any modifications in electrostatic screening of the longitudinal tip field upon entering the superconducting phase. We quench superconductivity using a magnetic field of 200 mT normal to the Pb(111) surface. By measuring force-distance curves and local field-emission resonance spectra at the same sample position in the presence and absence of the magnetic field, we constrain the change in screening between the normal and superconducting state to less than $\sim 1 \%$. This is between two to three orders of magnitude smaller than that predicted by Hirsch's theory, and entirely consistent with unmodified Thomas-Fermi screening across the superconducting transition.
CommentsMain: 5 pages, 4 figures; Supplementary: 4 pages, 6 figures
