Coherent Propagation and Many-Body Effects of Exciton Masses at Semiconductor Interfaces

本论文从实验和理论两方面研究了半导体中激子和声子的光致高密度效应及其在准二维界面上的相干传输，在BiI_3、GaSe和PbI_2层状晶体中研究了高密度激子质量的时空行为及其非线性光学响应。在BiI_3中，在高于阈值激发密度的时空分辨光致发光中，观察到二维堆垛层错界面（SFE）中激子的极大空间膨胀.由于激子质量从一个激发点相干输运到另一个激发点，样品表面上两个调谐到SFE态的激光光斑产生简并四波混频（DFWM）光，表明SFE极化激元质量处于玻色凝聚相。在GaSe和PbI_2中，强光激发引起了 ...更多信息 超晶格中的激子性质和相干声子现象，我们得到了以下结果：（1）超晶格中的激子性质和相干声子现象。(1)在GaAs/AlAs Ⅱ型超晶格中，电子和空穴分别在AlAs和GaAs层中空间分离，激发-双激子系统在衰减过程中的密度关系受玻色-爱因斯坦统计支配，导致双激子密度呈阈值状增加. (2)在GaAs/AlAs第I类超晶格中，揭示了从双激子到电子-空穴-等离子体相的转变过程，并与高密度载流子引起的带隙重整化有关。(3)在InAs/GaAs超晶格中，光激发的等离子体激元通过微带态与类GaAs相干LO声子耦合，我们从理论上研究了II型半导体量子阱威尔斯中激子相互作用的准二维玻色气体中的宏观量子现象，阐明了其有序态、元激发和相变机制。少

In our research, photoinduced high-density effects on excitons and phonons, and their coherent propagation at quasi tow-dimensional interfaces in semiconductors have been studied from experimental and theoretical aspects.In layered crystals BiI_3, GaSe, and PbI_2, we have studied spatial and temporal behavior of high-density exciton masses and their nonlinear optical responses. In BiI_3, extraordinarily large spatial expansion of the excitons confined in a tow-dimensional stacking fault interface (SFE) was observed in the space- and time-resolved photoluminescence above a threshold excitation density. The degenerate four-wave-mixing (DFWM) light induced by spatially isolated two laser-light spots tuned to the SFE state on the sample surface was emitted owing to the coherent transport of the exciton mass from one to the other exciting spot sites showing the SFE-polariton masses being in a Bose-condensed phase. In GaSe as well as PbI_2, it turned out that heavy photo-excitation brings ab … More out recoil luminescence due to scattering with the other excitons or carriers in competition with the biexciton formation.For the excitonic properties and coherent-phonon phenomena in superlattices (SLs), we have obtained the following results. (1) In GaAs/AlAs type-II SLs, where the electron and hole are spatially separated in the AlAs and GaAs layers respectively, the density relation of the excition-biexciton system in the decay process is dominated by Bose-Einstein statistics, which results in a threshold-like increase in the biexciton density. (2) In GaAs/AlAs type-I SLs, the transformation process from the biexciton to the electron-hole-plasma phase is revealed, connecting with the band-gap renormalization due to high-density carriers. (3) In InAs/GaAs SLs, the photoexcited plasmon couples with the GaAs-like coherent-LO phonon through the miniband state.We have theoretically studied macroscopic quantum phenomena in an interacting dilute quasi-two-dimensional Bose gas of excitons in a type-II semiconductor quantum wells and clarified its ordered states, elementary excitations and mechaisms of phase transitions. Less