Optical excitation of phase modes in strongly disordered superconductors
Optical excitation of phase modes in strongly disordered superconductors
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DOI：
10.1103/physrevb.89.174506
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发表时间：
2014-01
影响因子：
3.7
通讯作者：
T. Cea;D. Bucheli;G. Seibold;L. Benfatto;J. Lorenzana;C. Castellani
中科院分区：
文献类型：
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作者：
T. Cea;D. Bucheli;G. Seibold;L. Benfatto;J. Lorenzana;C. Castellani
根据Goldstone定理，连续U（1）对称性的破缺伴随着低能集体模的存在而沿着。在超导性的背景下，这些激发与超导（SC）序参量的相位有关，并且对于干净的系统是光学惰性的。在这里，我们表明，对于强无序超导体的相位模式获得的偶极矩，并出现作为一个subgap光谱特征的光学电导率。这一发现是获得与规范不变的随机相位近似方案的基础上的费米Bogoliubov-德Gennes状态，以及与一个原型的无序超导体的玻色子模型。在强无序状态下，系统显示出有效的SC特性粒度，光学活性偶极子连接到孤立的SC岛，为实现微波光学器件提供了新的视角。
According to the Goldstone theorem the breaking of a continuous U(1) symmetry comes along with the existence of low-energy collective modes. In the context of superconductivity these excitations are related to the phase of the superconducting (SC) order parameter and for clean systems are optically inactive. Here we show that for strongly disordered superconductors phase modes acquire a dipole moment and appear as a subgap spectral feature in the optical conductivity. This finding is obtained with both a gauge-invariant random-phase approximation scheme based on a fermionic Bogoliubov-de Gennes state as well as with a prototypical bosonic model for disordered superconductors. In the strongly disordered regime, where the system displays an effective granularity of the SC properties, the optically active dipoles are linked to the isolated SC islands, offering a new perspective for realizing microwave optical devices.