标题： 非常规超导体中集体模式的电流增强光学电导率 显示英文标题

标题： Current-Enabled Optical Conductivity of Collective Modes in Unconventional Superconductors

摘要： 我们理论上研究了具有非传统配对对称性的超导体中集体模式的电流驱动线性光导率。 在使用路径积分形式主义推导出具有多个配对通道和能带的超导体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。 利用竞争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式在注入超流时会在光学电导率中产生峰值。这包括单能带和多能带版本的Bardasis-Schrieffer模式、混合对称性Bardasis-Schrieffer模式以及Leggett模式。 利用带有Rashba自旋轨道耦合的带间p波超导性模型，我们发现在这种系统中，即使不引入超流，Bardasis-Schrieffer模式也是光学活性的。在p+ip手性基态中，这些模式最终会在纵向和横向光学电导率中产生峰值。 属于手性p+ip序参量的其他集体模式结果上不受自旋轨道耦合的影响，但在引入超流时会贡献于光学响应。 这些结果为在各种超导系统（包括多能带超导体和具有多个配对通道或多组分序参量的超导体，如手性p波或d波超导体）中观察集体模式提供了新的途径。 显示英文摘要

摘要： 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.