Nonlinear optical responses in noncentrosymmetric superconductors
Nonlinear optical responses in noncentrosymmetric superconductors
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DOI：
10.1103/physrevb.107.024513
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发表时间：
2022-05
影响因子：
3.7
通讯作者：
Hiroto Tanaka;H. Watanabe;Y. Yanase
中科院分区：
文献类型：
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作者：
Hiroto Tanaka;H. Watanabe;Y. Yanase
超导体中库珀对的量子凝聚所引起的独特的非互易响应一直受到人们的关注。近年来，基于Bogoliubov-de Gennes理论的非中心对称超导体的二阶非线性响应理论得到了发展。本文研究了时间反演对称超导体二阶光学响应的机制和条件。数值计算结果显示了超导态下的特征光电流和二次谐波产生。然而，超导诱导的非线性光学响应在对势的某些条件下消失。我们证明了带内和带间配对的共存是二阶超导光学响应的必要条件。此外，超导Berry曲率因子与超导态的Berry曲率分量有关，它对非线性响应是必不可少的。由此导出了超导非线性响应出现的微观条件。
The unique nonreciprocal responses of superconductors, which stem from the Cooper pairs' quantum condensation, have been attracting attention. Recently, theories of the second-order nonlinear response in noncentrosymmetric superconductors were formulated based on the Bogoliubov-de Gennes theory. In this paper, we study the mechanism and condition for second-order optical responses of time-reversal symmetric superconductors. The numerical results show the characteristic photocurrent and second harmonic generation in the superconducting state. However, the superconductivity-induced nonlinear optical responses disappear under some conditions on pair potential. We show that the coexistence of intraband and interband pairing is necessary for the second-order superconducting optical responses. In addition, the superconducting Berry curvature factor, which is related to a component of Berry curvature in the superconducting state, is essential for the nonlinear responses. Thus, we derived the microscopic conditions where the superconducting nonlinear response appears.