Effects of renormalization and non-Hermiticity on nonlinear responses in strongly correlated electron systems
Effects of renormalization and non-Hermiticity on nonlinear responses in strongly correlated electron systems
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DOI：
10.1103/physrevb.103.195133
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发表时间：
2021-05-17
影响因子：
3.7
通讯作者：
Peters, Robert
中科院分区：
文献类型：
--
作者：
Michishita, Yoshihiro;Peters, Robert
凝聚态的非线性响应提供了丰富的材料信息，具有在二极管或高频光学器件中应用的可能性，因而受到了广泛的研究。尽管非相互作用模型中的非线性响应已经得到了广泛的研究，但强相关性对非线性响应的影响仍然知之甚少，尽管已有研究表明相关性可以增强非线性响应。在这项工作中，我们首先利用格林函数方法对有限温度下的非线性响应进行了解析推导。然后，我们讨论了用传统的方法来考虑耗散的困难，如约化密度矩阵法。我们发现，在考虑光学响应时，弛豫时间近似导致了严重的限制。最后，我们证明了相关效应，如能带结构的重整化和轨道或亚晶格中不同的寿命，可以显著地增强非线性响应，甚至改变非线性电导的符号。
Nonlinear responses in condensed matter are intensively studied because they provide rich information about the materials and hold the possibility of being applied in diodes or high-frequency optical devices. While nonlinear responses in noninteracting models have been explored widely, the effect of strong correlations on the nonlinear response is still poorly understood, even though it has been suggested that correlations can enhance the nonlinear response. In this work, we first give an analytical derivation of nonlinear responses using Green's function methods at finite temperature. Then, we discuss the difficulties of considering dissipation using conventional methods, such as the reduced density matrix method. We reveal that the relaxation time approximation leads to severe limitations when considering optical responses. Finally, we demonstrate that correlation effects, such as the renormalization of the band structure and different lifetimes in orbitals or sublattices, can significantly enhance nonlinear responses and even change the sign of the nonlinear conductivity.