耦合量子阱中激子凝聚的研究进展

近年来，半导体量子阱中激子的玻色一爱因斯坦凝聚研究取得了很大进展．实验上利用耦合量子阱间接激子中电子和空穴在空间上的分离，显著提高了激子的冷却速度和寿命，成功地把激子冷却到1K以下，观察到了激子的准凝聚状态，并且在强激光照射下，发现了随光照强度增强而增大的激子发光环和环上形成的有规则斑点图案，引起了广泛的兴趣和重视．理论研究表明，发光环的出现是电子和空穴在量子阱中的反常输运行为造成的，但环上形成规则斑点的物理机理目前尚不清楚．文章介绍了这方面的实验背景和形成激子环的物理图像，指出了理论研究中存在的问题，并对解决问题的方案进行了讨论．

Progress in the study of exciton condensation in coupled quantum wells

Investigations on the Bose-Einstein condensation of excitons in semiconducting quantum wells have made great progress in recent years. In particular, the lifetime of indirect excitons has been dramatically improved by more than two orders of magnitudes by making use of the spatial separation of electrons and holes that form excitons in coupled quantum wells. This allows the excitons to be cooled down below 1K and the condensation or highly degenerate states of excitons to be realized experimentally. More recently, great attention has been attracted by the surprising observation of a photoluminescent ring of excitons, whose radius increases with increasing excitation power, and the fragmentation of this ring with a periodic pattern around a strong laser spot. It is now understood that the photoluminescence ring results from the extraordinary diffusion of electrons and holes in the coupled quantum wells. However, the mechanism leading to the formation of fragmented periodic patterns on the ring is still a puzzle. This paper gives a brief introduction to this field, with emphasis on the experimental facts and physical picture underlying the formation of these photoluminescent exciton rings. Existing problems in the theory and future directions for investigation are discussed.