Topological aspects of nonlinear excitonic processes in noncentrosymmetric crystals
Topological aspects of nonlinear excitonic processes in noncentrosymmetric crystals
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DOI：
10.1103/physrevb.94.035117
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发表时间：
2016-07-07
影响因子：
3.7
通讯作者：
Nagaosa, Naoto
中科院分区：
文献类型：
--
作者：
Morimoto, Takahiro;Nagaosa, Naoto
本文研究了非中心对称晶体中电场作用下的二级激子过程。本文利用Floquet理论和Keldysh绿色函数方法，推导出激子产生的位移电流和二次谐波的计算公式。结果表明，（i）稳定的直流位移电流的激子创建没有解离成自由载流子和（ii）二次谐波产生增强激子共振。所得到的公式澄清拓扑方面的这些二阶激子过程所描述的贝里连接的相关的价带和导带。
We study excitonic processes second order in the electric fields in noncentrosymmetric crystals. We derive formulas for shift current and second harmonic generation produced by exciton creation, by using the Floquet formalism combined with the Keldysh Green's function method. It is shown that (i) the steady dc shift current flows by exciton creation without dissociation into free carriers and (ii) second harmonic generation is enhanced at the exciton resonance. The obtained formulas clarify topological aspects of these second order excitonic processes which are described by Berry connections of the relevant valence and conduction bands.