在0.45- 4.2K温度范围内，研究了偶极激子的玻色-爱因斯坦凝聚下发光强度的相关性。利用GaAs/AlGaAs肖特基二极管单宽（25 nm）量子阱结构，在外加偏压下，将光激发的偶极激子收集在横向陷阱中.使用经典的Hanbury Brown - Twiss强度干涉仪（时间分辨率~0.4 ns）测量双光子相关性。在偶极激子的玻色凝聚阈值附近观察到光子“聚束”，该阈值由在光泵浦增加时激子凝聚的窄发光线的出现确定。双光子关联函数在系统相干时间尺度（<~1 ns）上呈现超泊松分布。在激发泵浦明显低于凝聚阈值时，没有观察到光子聚束。在激发泵浦增加到远高于阈值时，当激子凝聚体的窄线在发光光谱中生长时，光子聚束减少并最终消失-双光子相关器变为泊松，反映激子玻色凝聚体的单量子态起源。在相同的条件下，一阶空间相关器，测量从空间分离的冷凝物部分的发光干涉的装置，仍然显着。发现的光子聚束对温度相当敏感：从0.45 K到4.2 K，随着温度的升高，它下降了几倍。如果假设收集在横向阱中的偶极激子的发光直接反映了相互作用激子气体的相干性质，则在凝聚阈值附近观察到的光子聚束现象表明了相互作用激子玻色气体的相变。
英文摘要：
Correlations of luminescence intensity have been studied under Bose-Einstein condensation of dipolar excitons in the temperature range of 0.45-4.2 K. Photoexcited dipolar excitons were collected in a lateral trap in GaAs/AlGaAs Schottky-diode heterostructure with single wide (25 nm) quantum well under applied electric bias. Two-photon correlations were measured with the use of a classical Hanbury Brown - Twiss intensity interferometer (time resolution ~0.4 ns). Photon "bunching" has been observed near the Bose condensation threshold of dipolar excitons determined by the appearance of a narrow luminescence line of exciton condensate at optical pumping increase. The two-photon correlation function shows super-poissonian distribution at time scales of system coherence (<~1 ns). No photon bunching was observed at the excitation pumping appreciably below the condensation threshold. At excitation pumping increasing well above the threshold, when the narrow line of exciton condensate grows in the luminescence spectrum, the photon bunching is decreasing and finally vanishes - the two-photon correlator becomes poissonian reflecting the single-quantum-state origin of excitonic Bose condensate. Under the same conditions a first-order spatial correlator, measured by means of the luminescence interference from spatially separated condensate parts, remains significant. The discovered photon bunching is rather sensitive to temperature: it drops several times with temperature increase from 0.45 K up to 4.2 K. If assumed that the luminescence of dipolar excitons collected in the lateral trap reflects directly coherent properties of interacting exciton gas, the observed phenomenon of photon bunching nearby condensation threshold manifests phase transition in interacting exciton Bose gas.
Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons
人们认为分层玻色子偶极流体含有层间分子束缚态的凝聚物。然而，它的实验观察仍然难以捉摸。受最近两项实验工作的启发[Hubert等人，Phys. Rev. X 9，021026（2019）和D. J. Choksy等人，物理评论B 103 045126（2021）]，我们理论上研究，使用数值精确的量子蒙特卡罗计算，集体层间配对的实验签名在垂直堆叠的间接激子（IX）层。我们发现，IX能量转移与每一层的发展非平凡的密度不平衡的函数以下的非单调的趋势与跳跃不连续的密度平衡，确定与层间IX分子间隙。这种行为区分层间束缚对的超流性和不同层中独立的偶极凝聚。考虑到有限的温度和有限的密度不平衡的条件下，我们发现一个级联的Berezinskiii-Kosterlitz-无（BKT）的过渡，最初到一对超流，然后才在较低的温度下，到两个层的完全超流。我们的结果可以提供一个理论解释现有的实验观察在GaAs双量子阱（DQW）双层结构。此外，在未来的研究中，为了优化配对动力学的可见性，我们提出了一个分析，建议现实的实验设置在GaAs和过渡金属二硫属化物（TMD）双层DQW异质结构，集体层间配对和对超流性可以清楚地观察到。
