论文标题
观察非线性Meissner效应
Observation of the Non-linear Meissner Effect
论文作者
论文摘要
长期以来的理论预测是，在清洁的，非常规超导体中，磁穿透深度$λ$在零温度下，随磁场线性变化。这种非线性meissner效应是淋巴结状态同样重要的表现，就像研究经过良好的$λ$的线性线性依赖性，但从未有令人信服的实验观察到。在这里，我们介绍了节点超导体Cecoin $ _5 $和LAFEPO的测量值，该cecoin $ _5 $和LAFEPO清楚地显示了这种非线性Meissner效应。我们进一步展示了小型直流磁场对$λ（t）$的效果如何用来将间隙节点与非鼻深间隙最小值区分开。我们对KFE $ _2 $ as $ _2 $的测量表明，该材料具有这样的非鼻状状态。
A long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth $λ$, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally important manifestation of the nodal state as the well studied linear-in-$T$ dependence of $λ$, but has never been convincingly experimentally observed. Here we present measurements of the nodal superconductors CeCoIn$_5$ and LaFePO which clearly show this non-linear Meissner effect. We further show how the effect of a small dc magnetic field on $λ(T)$ can be used to distinguish gap nodes from non-nodal deep gap minima. Our measurements of KFe$_2$As$_2$ suggest that this material has such a non-nodal state.
