Spectroscopic evidence for the direct involvement of local moments in the pairing process of the heavy-fermion superconductor CeCoIn5
Spectroscopic evidence for the direct involvement of local moments in the pairing process of the heavy-fermion superconductor CeCoIn5
复制标题
局部矩直接参与重费米子超导体 CeCoIn5 配对过程的光谱证据
DOI：
10.1103/physrevb.103.224515
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发表时间：
2021
影响因子：
3.7
通讯作者：
Park, W. K.
中科院分区：
文献类型：
--
作者：
Shrestha, K.;Zhang, S.;Greene, L. H.;Lai, Y.;Baumbach, R. E.;Sasmal, K.;Maple, M. B.;Park, W. K.
重费米子超导体中电子配对的微观机制仍然是量子材料的主要挑战。某种形式的磁介导被广泛接受，其中自旋波动是主要候选者。还针对一些重费米子化合物提出了一种新颖的机制，即基于直接涉及电子矩的协同双通道近藤效应的“复合配对”。在中子散射测量中观察到的自旋共振峰的起源仍然存在争议，并且隧道电导中相应的驼峰倾斜结构缺失。这与铜酸盐和铁基高温超导体形成鲜明对比，在铜酸盐和铁基高温超导体中观察到两种特征信号，表明自旋涨落可能参与配对过程。在这里，我们报告了在较宽的温度和磁场范围内沿着三个主要晶体取向的平面隧道光谱的结果。配对间隙在远高于主体的位置处打开，并且其方向依赖性与对称性一致。随着磁场的增加，这种配对间隙如预期般受到抑制，但有趣的是，间隙状结构平稳地出现，线性增加直至施加的最高磁场。这种由场引起的间隙状特征仅在下面观察到。配对间隙和场致间隙特征的同时出现，及其随场的线性增加，表明电子局域矩直接参与配对过程。
The microscopic mechanism for electron pairing in heavy-fermion superconductors remains a major challenge in quantum materials. Some form of magnetic mediation is widely accepted with spin fluctuations as a prime candidate. A novel mechanism, “composite pairing” based on the cooperative two-channel Kondo effect directly involving the-electron moments, has also been proposed for some heavy-fermion compounds including. The origin of the spin-resonance peak observed in neutron-scattering measurements onis still controversial and the corresponding hump-dip structure in the tunneling conductance is missing. This is in contrast to the cuprate and Fe-based high-temperature superconductors, where both characteristic signatures are observed, indicating spin fluctuations are likely involved in the pairing process. Here, we report results from planar tunneling spectroscopy along three major crystallographic orientations ofover wide ranges of temperature and magnetic field. The pairing gap opens at, well above the bulk, and its directional dependence is consistent withsymmetry. With increasing magnetic field, this pairing gap is suppressed as expected but, intriguingly, a gaplike structure emerges smoothly, increasing linearly up to the highest field applied. This field-induced gaplike feature is only observed below. The concomitant appearance of the pairing gap and the field-induced gaplike feature, along with its linear increase with field, indicates that the-electron local moments are directly involved in the pairing process in.