Space-resolved luminescence and degenerate four-wave-mixing spectra of heavily photo-created exciton states in a layered crystal GaSe
Space-resolved luminescence and degenerate four-wave-mixing spectra of heavily photo-created exciton states in a layered crystal GaSe
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层状晶体 GaSe 中重光产生激子态的空间分辨发光和简并四波混合光谱
DOI：
10.1016/s0022-2313(99)00313-0
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发表时间：
2000
影响因子：
3.6
通讯作者：
V. Aguekian
中科院分区：
文献类型：
--
作者：
M. Yamamoto;H. Mino;I. Akai;T. Karasawa;V. Aguekian
利用光致发光和简并四波混频信号研究了高密度对层状GaSe单晶中激子态的影响。由于弱束缚激子态在强激发下的占位效应，最低激子态的发光峰从较低能量向激子的较高吸收峰移动。对于较重的激发，由于激子-激子和激子-载流子散射的反冲（红移）发光成为主导。在重激发下，自由激子在空间和时间分辨发光谱上表现出明显的空间传播，群速度为103 × 108 cm/s。低激发密度下具有单指数衰减的时间相关DFWM信号在高激发密度下由于多体效应而具有多个分量。在负时域，DFWM信号揭示了激子分子态的响应。从负时域的DFWM谱估计出激子分子的结合能为1.8meV。
High-density effects on the exciton states in a layered GaSe single crystal have been studied by observing photoluminescence and degenerate four-wave-mixing (DFWM) signals. The luminescence peak of the lowest exciton states shifts from lower energy to the higher lying absorption peak of the exciton owing to the site-filling effects of the weakly bound exciton states under heavy excitation. For heavier excitation, the recoil (red-shifted) luminescence due to exciton–exciton and exciton–carrier scattering becomes dominant. The free exciton shows remarkable spatial propagation under the heavy excitation on the space- and time-resolved luminescence spectra, giving a group velocity ∼3×108cm/s. The time correlated DFWM signals having a single exponential decay for lower excitation densities come to have multiple components due to many-body effects under higher excitation densities. In the negative time domain, the DFWM signals reveal the response from the excitonic molecule states. From the DFWM spectra in the negative time domain, the binding energy of the excitonic molecule is estimated to be ∼8meV.