Title: Current-Enabled Optical Conductivity of Collective Modes in Unconventional Superconductors Show Chinese title

Title: 当前驱动的集体模态在非传统超导体中的光学电导率

Abstract: We theoretically investigate the current-enabled linear optical conductivity of collective modes in superconductors with unconventional pairing symmetries. After deriving general formulas for the optical conductivity of a superconductor featuring multiple pairing channels and bands using the path integral formalism, we apply these formulas to several models. Using a model of competing s- and d-wave pairing interactions, we find that several known collective modes generate peaks in the optical conductivity upon injection of a supercurrent. This includes single- and multiband versions of Bardasis-Schrieffer modes, mixed-symmetry Bardasis-Schrieffer modes, and Leggett modes. Using a model for interband p-wave superconductivity with Rashba spin-orbit coupling, we find that in such a system Bardasis-Schrieffer modes are optically active even without introducing a supercurrent. In a p+ip chiral ground state, these modes turn out to produce peaks in the longitudinal and transverse optical conductivity. Other collective modes belonging to the chiral p+ip order parameter turn out to be unaffected by the spin-orbit coupling but contribute to the optical response when a supercurrent is introduced. These results promise new avenues for the observation of collective modes in a variety of superconducting systems, including multiband superconductors and superconductors that feature multiple pairing channels or multi-component order parameters, such as chiral p- or d-wave superconductors. Show Chinese abstract

Abstract: 我们理论研究了具有非常规配对对称性的超导体中集体模态的电流增强线性光学电导率。 在使用路径积分形式推导出具有多个配对通道和能带的超导体的光学电导率的一般公式后，我们将这些公式应用于几个模型。 使用一个竞争s波和d波配对相互作用的模型，我们发现几种已知的集体模态在注入超电流时会在光学电导率中产生峰。 这包括单带和多带版本的Bardasis-Schrieffer模态、混合对称性Bardasis-Schrieffer模态以及Leggett模态。 使用一个具有Rashba自旋轨道耦合的带间p波超导体模型，我们发现在这种系统中，即使不引入超电流，Bardasis-Schrieffer模态也是光学活跃的。 在p+ip手征基态中，这些模态显示出纵向和横向光学电导率的峰。 属于手征p+ip序参量的其他集体模态似乎不受自旋轨道耦合的影响，但当引入超电流时会对光学响应有所贡献。 这些结果为在各种超导系统中观察集体模态提供了新的途径，包括多带超导体以及具有多个配对通道或多组分序参量的超导体，如手征p波或d波超导体。