Butov L V, Gossard A C, Chemla D S
Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, University of California, 94720, USA.
Nature. 2002 Aug 15;418(6899):751-4. doi: 10.1038/nature00943.
There is a rich variety of quantum liquids -- such as superconductors, liquid helium and atom Bose-Einstein condensates -- that exhibit macroscopic coherence in the form of ordered arrays of vortices. Experimental observation of a macroscopically ordered electronic state in semiconductors has, however, remained a challenging and relatively unexplored problem. A promising approach for the realization of such a state is to use excitons, bound pairs of electrons and holes that can form in semiconductor systems. At low densities, excitons are Bose-particles, and at low temperatures, of the order of a few kelvin, excitons can form a quantum liquid -- that is, a statistically degenerate Bose gas or even a Bose-Einstein condensate. Here we report photoluminescence measurements of a quasi-two-dimensional exciton gas in GaAs/AlGaAs coupled quantum wells and the observation of a macroscopically ordered exciton state. Our spatially resolved measurements reveal fragmentation of the ring-shaped emission pattern into circular structures that form periodic arrays over lengths up to 1 mm.
存在多种量子液体，如超导体、液氦和原子玻色 - 爱因斯坦凝聚体，它们以涡旋有序阵列的形式表现出宏观相干性。然而，在半导体中对宏观有序电子态进行实验观测仍然是一个具有挑战性且相对未被探索的问题。实现这种状态的一种有前景的方法是使用激子，激子是在半导体系统中能够形成的电子和空穴的束缚对。在低密度下，激子是玻色子，在几开尔文量级的低温下，激子可以形成量子液体，即统计简并的玻色气体甚至玻色 - 爱因斯坦凝聚体。在此，我们报告了对 GaAs/AlGaAs 耦合量子阱中准二维激子气体的光致发光测量以及对宏观有序激子态的观测。我们的空间分辨测量揭示了环形发射图案分裂成圆形结构，这些圆形结构在长达 1 毫米的长度上形成周期性阵列。
