Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN
Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN
复制标题
超导 NbN 中超电流注入红外激活希格斯模式
DOI：
10.1103/physrevlett.122.257001
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发表时间：
2019
影响因子：
8.6
通讯作者：
Shimano Ryo
中科院分区：
文献类型：
--
作者：
Nakamura Sachiko;Iida Yudai;Murotani Yuta;Matsunaga Ryusuke;Terai Hirotaka;Shimano Ryo
超导体中的希格斯模式，即，序参量的集体振幅模式既不与电荷也不与自旋涨落相关联，因此在线性响应状态下它不耦合到电磁场。与这种普遍的理解相反，在这里，我们证明，如果直流超电流被引入到超导体，希格斯模式成为红外活跃，并直接观察到的线性光学电导率测量。我们观察到一个尖锐的共振峰在薄膜NbN在直流超导电流的存在下的光学电导率谱，表现出合理的协议与最近的理论预测。这项工作所证明的方法为研究各种超导体中的希格斯模式开辟了一条新的途径。
The Higgs mode in superconductors, i.e., the collective amplitude mode of the order parameter, does not associate with charge nor spin fluctuations, therefore it does not couple to the electromagnetic field in the linear response regime. Contrary to this common understanding, here, we demonstrate that if the dc supercurrent is introduced into the superconductor, the Higgs mode becomes infrared active and is directly observed in the linear optical conductivity measurement. We observed a sharp resonant peak atin the optical conductivity spectrum of a thin-film NbN in the presence of dc supercurrent, showing a reasonable agreement with the recent theoretical prediction. The method as proven by this work opens a new pathway to study the Higgs mode in a wide variety of superconductors.