高密度e-h系统超辐射发射期间长程序形成的观测
Observation of the formation of long-range order during superradiant emission in a high-density e-h system
摘要：
从原子、电子或电子-氢体系到量子相的转变是一个特殊的过程，系统的微观和宏观性质都发生了根本性的变化。玻色-爱因斯坦凝聚，已经在许多物理系统中观察到，包括超冷原子气体和固态准粒子。平衡凝聚最典型的例子是金属中库珀对的超导态。然而，在许多情况下，所研究的粒子或准粒子的寿命是有限的，从皮秒到毫秒不等。即使在这种情况下，冷凝也是可能的。目前普遍认为，凝聚量子态最重要的特征是密度矩阵中的相干性和非对角长程序。在微观距离上建立的相位相干性是所有玻色凝聚体的固有性质。两个凝聚体或同一凝聚体的两个独立部分之间的干涉实验通常被认为比观察基态的宏观占据更有说服力。长程序和空间相位相干性的形成可以通过使用迈克耳孙干涉仪或杨氏双缝装置研究干涉图案来测量。本文介绍了在室温下观察GaAs中高密度电子-氢系统在飞秒超辐射产生过程中宏观有序态的长程时空相干性的实验结果
英文摘要：
The transition of atomic, electronic, or e-h systems to quantum phases is an extraordinary process when both microscopic and macroscopic properties of the system undergo fundamental changes. Bose-Einstein condensation, has been observed in a number of physical systems, including super-cold atomic gases and solid- state quasiparticles. The most typical example of equilibrium condensation is the superconducting state of Cooper pairs in metals. However, in many cases the lifetime of particles or quasiparticles under study is finite, ranging from picoseconds to milliseconds. And even in this case condensation is possible. It is generally understood at present that coherence and off-diagonal long-range order in the density matrix are the most important characteristic features of condensed quantum states. Phase coherence established over microscopic distances is an intrinsic property of all Bose condensates. Experiments featuring interference between either two condensates or two separate parts of the same condensate are often considered as more convincing than observation of the macroscopic occupation of the ground state. The formation of long-range order and spatial phase coherence can be measured by studying interference patterns using either a Michelson interferometer or Young double slit arrangement. Here we present experimental results of observation of long-range temporal and spatial coherence of a macroscopically ordered state of a high-density e-h system in GaAs during the generation of femtosecond superradiant emission at room temperature
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