半导体中激子相干关联光谱的态和与准粒子图像;多维NMR的飞秒模拟
Sum-over-states vs quasiparticle pictures of coherent correlation spectroscopy of excitons in semiconductors; femtosecond analogues of multidimensional NMR
摘要：
基于激子对超快脉冲序列的非线性光学响应的二维相关光谱（2DCS）具有提供半导体中载流子动力学的一些独特见解的潜力。2DCS最突出的特征，交叉峰，可以最好地理解使用涉及多体本征态的状态求和图。然而，半导体的光学响应通常通过求解动力学变量的截断运动方程来计算，这导致准粒子图像。在这项工作中，我们推导出格林函数表达式的四波混频信号产生的各个相位匹配方向，并使用它们来建立两个图片之间的连接。指出了与Frenkel激子（硬核玻色子）和振动激子（软核玻色子）的形式联系。
英文摘要：
Two-dimensional correlation spectroscopy (2DCS) based on the nonlinear optical response of excitons to sequences of ultrafast pulses, has the potential to provide some unique insights into carrier dynamics in semiconductors. The most prominent feature of 2DCS, cross peaks, can best be understood using a sum-over-states picture involving the many-body eigenstates. However, the optical response of semiconductors is usually calculated by solving truncated equations of motion for dynamical variables, which result in a quasiparticle picture. In this work we derive Green's function expressions for the four wave mixing signals generated in various phase-matching directions and use them to establish the connection between the two pictures. The formal connection with Frenkel excitons (hard-core bosons) and vibrational excitons (soft-core bosons) is pointed out.
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